The London Mobilisation Centres

Alec Beanse and Roger Gill



The London Mobilisation Centres were a somewhat varied group of structures erected between 1889 and 1903 as part of the London Defence Scheme. Although the centres primary role within the scheme was that of storehouse, most were fortified and some would have been able to take an active part in resisting an assault, supporting the fieldworks that were to be the main line of defence for London. For a group of structures with a common purpose they exhibited wide variation in layout and size. This article will look at London Defence Scheme and examine the design of the Centres themselves.



The defence of England against invasion had always been of importance and had, in the main, been achieved by a combination of coast defences and a strong Navy. As a consequence of this policy London, unlike other major cities in Europe, was never provided with any defences of its own.

While ships were dependant on the wind, the choice of landing places was somewhat restricted and this worked in favour of the defence. Things were complicated when steam power was adopted, no longer constrained by the elements the choice of landing places multiplied making the task of resisting an invasion much harder. Coincident with the introduction of steam was a progressive loss of confidence in the Royal Navy and its ability to prevent an invasion. This was mainly a result of large ship building programmes instituted by potential enemies, notably France.

That London was not provided with its own defences until the announcement of the London Defence Scheme in 1889 was not for want of trying, however. An early proposal for defending London was in response to a French invasion scare in 1803. During a debate in Parliament on the provision of defences Pitt said: "If by erection of earthworks such as I am recommending, you can delay the progress of the enemy for 3 days it may make the difference between the safety and the destruction of the Capital". As was so often to be the case, nothing was done.


Sir George Murray published a set of proposals in 1845. He wanted a broad deep ditch with bastioned ramparts between Vauxhall Bridge and Deptford. To the north his line was to have run from Chelsea Creek through Hampstead, Highgate and Stamford Hill. Recognising the importance of the Arsenal at Woolwich, Murray advocated that it should have its own system of defence. While Wellington appeared, on the face of it, to support Murray's proposals and even suggested that Woolwich should be included in the system, he really felt that preventing a landing was the best solution. Murray's proposals, like so many others, were to come to nothing.


The official view remained that fixed defences for the capitol were undesirable. The then Inspector General of Fortifications, J. F. Burgoyne, observed in 1856 that fixed defences "would never be assented to and the greater part of which I do not see the advantage".

Perhaps the first serious attempt to provide fixed defences for London was in 1859 when the then Major Drummond-Jervois, in his capacity as secretary to the Royal Commission on the Defence of the United Kingdom, submitted proposals for a ring of forts around the capitol some 53 miles long. The forts along this line would have been 800 yards apart, typically of 25 guns and 250 men. As an alternative, should this be rejected, he proposed a smaller perimeter to protect the Royal Arsenal at Woolwich. The estimated cost of the first proposal then was £5,000,000 and for the Woolwich scheme £1,300,000.


It was not surprising that both were rejected by the Commission, especially when you consider the total for the defences proposed for the nine main ports was only £4,100,000. The Commission did, however, recommend one fort on Shooters Hill overlooking the Arsenal, though in the event this was never built anyway. Doubtless the Commission, having recommended a vast programme of coast defences, felt that London would not come under threat as any attempted invasion would have been repulsed. When complete, however, the programme recommended by the Royal Commission would have actually made attack on London more likely. If an aggressor had landed somewhere in the south-east, with all major harbours well defended, London would have made an attractive target with no fixed defences to overcome.


Jervois did not let his London proposals rest there however and carried on planning for the defence of the capitol. At the time the only maps available of the area were 1 inch Ordnance Survey Maps and Sir Henry Stokes (Secretary for Military Correspondence) recommended that a detachment of Royal Engineers, under Jervois' control should make a survey and produce more detailed maps. These maps covered an area from Chatham via Reigate and Guildford to Reading at a scale of 6 inches to 1 mile. They contained a wealth of topographical detail and were doubtless used later when planning the London Defence Scheme. Permission was later given to extend work to Essex and subsequently the earlier maps were revised.

Once the maps were made, Drummond-Jervois requested the use of a Royal Engineers Officer and two Draughtsmen to prepare plans for extemporised works to be constructed in event of an invasion, these plans to be held as a confidential document at the War Office. This request was approved on the 22nd November 1870, although two junior officers were substituted for the two draughtsmen.


It would seem that Jervois had not given up on the idea of a ring of permanent works either as a map of London, marked on the back "Plan to accompany Report on Proposed Line for Permanent Defences around London. Wm. J. Drummond-Jervois 6th April 1875" ,would indicate. This showed a total of 89 sites for works indicated along the 93 mile length of the line. There was also a reduced perimeter shown with 34 sites along its length.

In 1875 a Mobilisation Scheme for the defence of England was produced by Colonel Home and assumed a warning period of 6 weeks. This Scheme was based on the premise that there was, or would be, a chain of fortified positions around London and that the assumed period of 6 weeks available for preparations would have allowed the construction of works of respectable strength.


Throughout the 1880's General Sir Edmund Hamley, MP for Birkenhead, pressed strongly for measures to prevent an invasion. He was concerned that the substantial naval construction being undertaken by both France and Russia would diminish the ability of the Royal Navy to prevent invasion. A strong supporter of the Volunteer Movement, Hamley advocated the construction of a series of lightly fortified assembly points around London for the Volunteers to assembly at on a general mobilisation. He felt that the Volunteers, lacking experience, would perform better when under fire from fixed positions rather than going into battle alongside the regulars.


Major Elsdale came up with a set of proposals, "The Defence of London and England", that were published in the Royal United Services Institute Journal in 1886. He proposed a line that followed that previously suggested by Neugent: - Watford, Broxbourne, between Epping and Ongar, passed Romford to the North Downs, Dorking, Weybridge, Staines, Uxbridge and back to Watford. An extension was proposed to Chatham, then up to Tilbury and back along the Thames to meet the above line. The Armament proposed was to be not less than 180 powerful guns of position, ideally the 4 inch BL of 22 hundredweight. To support these guns, permanent magazines were to be built at not more than 5 mile intervals. These would be stocked with shells although the cartridges would only be added in time of war. In addition 300 Machine Guns, 10 barrelled Nordenfelts or 5 barrelled Gardeners, should be issued to the Volunteers and there would also be Automatic Land Torpedoes, Mines and Fougasses. Picks and Shovels, Woodman's Tools, Sandbags and Iron Wire for Obstacles would also be stored. Caponiers would be constructed ahead of the works, protected from direct fire by an earth bank forming a 'T' shape, allowing machine-guns to give flanking fire. Redoubts would be constructed, retired from the main front as back-up to the works in event of them being over-run. He also thought that good roads would be needed, ideally a Military Road around the whole position to allow rapid movement of supplies and troops.


When John Ardagh, the DMI, produced his "Defence of England: Mobilisation of regular and auxiliary forces for Home Defence" in 1888 he commented of the 1875 Mobilisation Scheme:- "Now, however, we cannot count on so long a grace; a week at the outside may be at our disposal and until there is a line of defences interposed between London and the invader, it will be indispensable to put all our forces in the line to oppose him."


His scheme was:- "for three Army Corp, two in the Weald of Sussex/Kent south of the chalk scarp and one in Colchester. Between these and London is the whole of the Volunteer Army less those told off to the Garrisons". Ardagh recognised the desirability of works around London but concluded that:- "as this line does not exist in time of peace, in emergency only imperfect substitutes could be erected and the extemporised line would be weak and liable to be forced". He proposed the construction of: "six entrenched camps at Aldershot, Caterham, Chatham, Tilbury, Warley & Epping where storehouses and magazines will have been constructed within and in some cases a few of the works constructed as well. The designs for those which cannot be commenced until the emergency arises will be held in readiness and issued to contractors to execute."


Later the same year Ardagh produced another paper regarding the Defence of London in which he advocated the construction of 30 forts each containing 30 guns costing about £100,000 each. In addition to London, which accounted for 25 of the 30, the Dedham was to have 2 with the remaining 3 located in the Harwich area. Planning was also undertaken for a bridge and steam ferry at Gravesend during an emergency.


In May 1888 a deputation of M. P.'s approached the Secretary of State for War, Edward Stanhope, on the subject of National Defence. In reply, following reference to a mobilisation scheme produced by General Brackenbury in 1886 and stating the need to organize and utilise existing forces to the full, Stanhope went on to say:-

"It is to this that our attention is at the present time directed, and our object may said to so organize these multifarious forces as to be able to produce at shot notice a field army sufficient to defend England , and primarily to protect London. I have been heartily glad to see the attention which had been bestowed upon the proposals put forward on this subject by Sir Edward Hamley. We are working out in detail, and as rapidly as possible, a scheme for this purpose. It is not one which necessarily involves the expenditure of much money, though what is immediately necessary is being found, but it does require patient and persevering organisation. You would not expect me to make public any details of the plan, but it may be explained generally as follows".


He then described the proposed organization of a third Army-Corp formed from a mix of Regulars and Militia, to be supported by all Volunteers not required for other duties. On mobilization these forces would assemble at predefined points from where they would occupy the lines to be defended. The Volunteer Artillery was seen as making a significant contribution this plan and it was hoped to issue them with 250 mobile and 80 heavier guns. He concluded by saying:-

"In answer, therefore, to the question which you have put to me, it is a satisfaction to be able to say that we are making some progress in the direction which you desire."


The London Defence Scheme

The London Defence Scheme was formally announced in a speech on estimates to Parliament by Edward Stanhope, Secretary of State for War, in March 1889 in which he outlined steps that were to be taken to implement Hamley's proposals. He went on to ask members of the house not to press him for details in the national interest.


That something was finally done has much to do with the perceived weakness of the Royal Navy at that time. France and Russia were building up their fleets such that the Royal Navy did not have the superiority it had hither to enjoyed. An additional complication for the defence was the change taking place in ship design. Sail had, by now, given way to steam propulsion allowing an invader a much greater choice of time and place for a landing, ships now being largely independent of wind and current. This deficiency in numbers was addressed, simultaneously with the London Defence Scheme, by the passing of the Naval Defence Act of 1889 which instituted a large shipbuilding programme.

A further consideration was the completion of the defences recommended by the 1860 Royal Commission. All the major ports were now well defended against attack by land or sea and could only be taken by siege. This left on one attractive target for an invader, to march on London, overpower it and thus take the country.


In January 1897 Ardagh produced his "Memorandum on the (So Called) Authorised Scheme of Defence, and on The Defence of London 1897".

In this he first outlined earlier proposals:- "The Duke of Wellington and Mr Pitt, Lord Palmerston and Sir John Burgoyne, in bygone days have advocated measures for the defence of the metropolis, which may be summed up in the words of the great Duke, as "An army in the field, aided by all the means of fortification which experience in war, and science can suggest".


He went on to note that Stanhope made a statement to the Committee of the House of Commons, on the Army Estimates, 11th March 1889 describing in outline a second line of defence between the coast and London.


As to the current position he observed that: "13 sites have been purchased for 25000l and an equal sum expended on works and roads upon 3 of them. Each work contains storage accommodation for the gun and small arms ammunition required for the Volunteer Batteries of Position and the infantry allowed for the defence of the neighbourhood as well as tools and camp equipment.

The sites which have been purchased are situated as follows:-

1 Epping (North Weald)

2 Farningham

3 Halstead

4 Betsom's Hill (Westerham)

5 Woldingham

6 Foster Down (Caterham)

7 East Merstham

8 West Merstham

9 Reigate

10 Betchworth

11 Dorking (Box Hill)

12 Dorking (Denbies)

13 Guildford (Pewley Hill)

14 Guildford (Henley Grove)

(NOTE: The conflict in the number of sites is due to the inclusion of West Merstham in the list. This site was not purchased, clearance rights only were obtained.)


Several schemes for the defence of London by permanent forts have from time to time been advocated by our military advisors but have never met with support from the country at large; the opposition being mainly on the grounds of expense, which would amount to at least 3,000,000l.

Our proposals are identical with those initiated by Mr Stanhope are of a far more modest description and only contemplate the construction of entrenchments when the necessity arises, upon sites previously selected , and according to plans previously prepared , around the nuclei in which our Volunteer brigades and batteries will find already stored their reserve ammunition for both guns and rifles, their tools and equipments necessary for the emergency.


While our field army will be ready to engage the enemy at any point where he may appear, we look to a portion of the volunteers to form a second line of defence between London and the coast; and we shall spare no effort to enable them to fight upon the strongest positions, and under the most favourable conditions".


A brief description of the history of the scheme finally adopted is given in the Handbook For The London Defence Positions, War Office 1903 (Provisional):-

"1. The origin of the scheme was a memorandum, drawn up in 1888, by Col Ardagh, A.A.G., explaining the importance of the subject, and suggesting the acquisition of 30 sites, where small works, capable of expansion, might be built, forming "points d'appui" for entrenched positions, which it might subsequently be desired to construct, would bar important roads and act as store houses for entrenching tools and ammunition. He considered that at least a week would be available for entrenching the necessary positions, and proposed to draw up projects for their preparation, to be entrusted for execution to the Railway and Engineer Volunteer Staff Corps, under the Inspector General of Fortification.


2. The acquisition of certain sites where storehouses, or so-called "Forts" have since been built, was sanctioned in 1889, and in 1890, a committee of three officers was appointed to draw up a scheme for the occupation of the defensive line around London. They were told the number of troops that were to be made available, their places of concentration, and the position of the "Forts" which it had been decided to erect: and they were required:-

(1) To examine the line of the chalk ridge from Guildford, by the Darenth Valley, to Dartford; and, north of the Thames, a line from Vange, by Brentwood, to North Weald.

(2) To determine the probable points of passage of those lines by an invader.

(3) To prepare detailed schemes, showing the tactical disposition of units:-

(a) Assuming the point of passage to be held in force by the following strength, viz.:-

If south of the Thames-Two Army Corps, plus the Volunteers concentrating within the defended front of that position, as well as half the remaining Volunteers concentrating south of the Thames.

If north of the ThamesTwo Army Corps, plus all the Volunteers concentrating north of the Thames.

3. The work of this committee was completed in March, 1892, and forms the basis of the present arrangements."

The committee had been very thorough and produced the following documentation:

"1. A general report south of the Thames.

2. A general report north of the Thames

3. Two maps and reports on the lateral communications for north and south of the Thames.

4. Detailed reports on the preparation and occupation of the selected positions.

5. A series of maps, at a scale of 6 inches to the mile, showing the proposed dispositions, entrenchments, clearances, etc. for each position.

Following on from this, working plans for the strong points, trench profiles and so forth together with instructions for the officers preparing sections of the defences were prepared."


It was envisaged that in the event of an invasion the regular army would move to bring the aggressor to battle close to the landing place once his line of advance was known. In the meantime the London Defence Positions would be prepared by civilian contractors, supervised by Volunteer Royal Engineers, in accordance with the already prepared plans. If work was not proceeding fast enough the Volunteers would assist to ensure speedy completion, using the tools held in the centres. The original intention was for the Volunteers to prepare the positions themselves, the change to the use of civilian labour occurring in 1900. All the major construction contractors were interviewed to ascertain the number of navvies they could supply.

A committee considering the construction of the positions in 1901 recommended that the Inspector General of Fortification be made responsible for the execution of the necessary works. This included preparation and maintenance of the plans, control of the civilian labour which included their transportation, housing and feeding and for the provision of tools. It was a requirement that the work should be completed on the eighth day after the issue of the order to commence the work.


Starting 5 miles west of Guildford along the Hog's Back the line proposed followed the ridge of the North Downs to Knockholt where it was to turn up the western side of the Darenth valley to the Thames at Dartford. North of the Thames it was to recommence at Vange, then by way of Laindon, Brentwood and Kelvedon Hatch to Epping. The line to be entrenched was divided into ten sectors totalling 72 miles in length, 48 miles south and 24 miles north of the Thames. Most sectors were supported by a Mobilisation Centre or Centres where the ammunition and tools for that sector were housed. Two of the sectors, Guildford and Darenth, were to have entrenchments prepared on their left flanks, but not occupied initially. These were known as the Shere and Darenth Valley Extensions, 4 miles and 3¾ miles long respectively. In addition, at Guildford, Dorking and Red Hill there were to be advanced positions across part of the front, between ½ to 3 miles in advance of the main positions. An additional position, 4 miles in length, was to be formed on the high ground overlooking the village of Wrotham. Manned by one division, this was seen as a link to the Chatham defences as well as covering the proposed bridge at Gravesend. It also would have hindered any flanking movement on Farningham or Dartford. The Handbook considered it possible that when next revised the defensive line would be continued across to Chatham rather than up the Darenth Valley. When complete, the defensive positions were to be occupied by the Volunteers following their mobilisation.


While these preparations were in hand, arrangements for distribution of ammunition and supplies would be put in motion. London was seen as the base of operations in which three main depots were to be established, at Bishopsgate and Nine Elms Goods Stations and the Supply Depot at Woolwich. From these places the stores would have been moved by rail to advanced depots, set up at previously identified railway stations, then on to supply parks for distribution to the defence positions. In the reverse direction, these arrangements would serve for evacuation of the wounded to base hospitals that would have been set up in public and other building in London. Work would also commence on the Bridge of Boats at Tilbury, allowing rapid movement of reinforcements north or south of the Thames as the tactical situation demanded.


Thus, in the event that the regular army was overcome in the field, it could fall back on the prepared defensive positions already manned by the Volunteers. Particular attention was given to the principal routes that an invader might take, such as the gaps in the North Downs.

That nothing was done to provide fixed defences for London until 1889 is probably just as well. Had earlier proposals been implemented, the defences provided would have become quickly outmoded. The rapidly increasing range of artillery would have permitted any attacker to bombard London from the high ground surrounding it, the defenders powerless to intervene. Also, London was a growing city and expansion would have led to buildings outside the enceinte, providing cover for an attacker unless demolished.


An initial rush of enthusiasm saw acquisition of land, the construction of North Weald and the stores at Caterham, Tilbury and Warley by 1890 followed by Halstead and Pewley Hill by about 1895. There was then a gap of five years or so before the remaining centres were completed. Money, as today, was a problem: -"By 1st April 1891 the whole of the selected sites around London with the exception of Reigate will have been purchased. Only one work however, namely that at North Weald, is complete no money being at present available for the erection of any others." This shortage of funds, and the loss of Hamley's drive following his death in 1893, resulted in this construction programme being dragged out until 1903. The time taken to complete the construction of the mobilisation centres would suggest that it was not being taken that seriously. In any case there was never any attempt to relate the training of the Volunteers so that they could become familiar with what would be expected of them in event of an invasion.

Barely had the centres been completed than further work was needed at some locations to provide additional ammunition storage capacity. This followed the re-equipping of the Volunteer Artillery with breech loading guns and this work was not completed until 1904/05.


The Navy Defence Act of 1889 had instigated a large shipbuilding programme aimed at restoring the Royal Navy's former pre-eminent position. In a few years the perceived weaknesses of the Royal Navy had been redressed and by the early 1900's the risk of invasion was considered negligible. As a result, at the 85th meeting of the Committee on Imperial Defence on 9th March 1906 the scheme was officially abandoned, subject to Naval Supremacy being maintained. Rather than dispose of all the Centres immediately, it was suggested that as increased ammunition storage capacity was going to be required for the Horse & Field Artillery, a few conveniently located centres be retained to accommodate it. In any case it would have been difficult to absorb the large quantity of ammunition and stores held in the centres immediately, retaining some centres would have allowed a more orderly removal of the items held.


As a consequence of this decision a majority of the centres were quickly sold off. A few, however, were retained until after World War I suggesting that they were indeed used for ammunition storage as indicated previously. In the case of Fort Halstead, an ammunition laboratory was subsequently added within the fort in 1915.and a store building outside in 1920.


During World War I, part of the London Defence Positions was resurrected to form the inner stop line in the event of a German invasion. There were some changes though, north of the Thames the line was continued to the River Lea at Broxbourne rather than stopping at Epping as previously. South of the Thames, instead of running up the Darenth Valley from Knockholt, it was continued to Halling, by way of Wrotham, thus linking to the Chatham defences. This mirrored proposals in the original scheme that were never implemented. At the western end the line was stopped short at Buckland Hill, to the north-west of Reigate, just beyond the Reigate mobilisation centre.


Further use was made of the Centres in World War II, most notably Fort Halstead which was repurchased by the War Office in 1937 and initially modified as a filling plant for the 3inch Anti-Aircraft Rockets. An armament research facility then gradually built up around the former Centre throughout the war years. This site remained in Government hands post war and eventually became known as the Royal Armament Research & Development Establishment (RARDE).


North Weald formed part of the defences of the now defunct Ongar Radio Station that had grown up around it between the wars. Two Allen-Williams Turrets were added to the Redoubt, one on each flank. The site was classified as a Vulnerable Point and garrisoned by VP Troops.

Also thought to have been used, probably by Home Guard, were Henley Grove, Westerham and Reigate.



When viewing the centres, it is important to see them in their correct context. The London Defence Positions, from where the defence was to be conducted, were the fieldworks to be constructed in the week's grace expected before an invader would be in a position to launch an attack London. As well as positions for artillery a number of infantry redoubts were to have been constructed and in one case a lunette! (probably the last usage of this term) The centres themselves had two distinct roles in the scheme of things. First they were to act as store houses holding an initial supply of ammunition for the units who would man the defences and tools to aid in the construction of said defences. Secondly, upon invasion and once the main defence line was constructed, they could be used as strong points to fall back on if the line was breached locally. A few centres, notably Halstead and North Weald, were positioned so as to take an active part in the defence by virtue of their location and the ability to mount field artillery or machine guns.


Although there was little similarity in layout between individual centres, an almost common factor was the adoption of the Twydall Profile in their design. This was adapted in the case of some centres resulting in a more compact trace than in the original concept. Perhaps the outstanding examples of the use of the Twydall Profile were the centres at Farningham and North Weald where the concept was taken a stage further. At both of these centres two tunnels ran from the interior of the works, under the rampart and gave access to the ditch at Farningham and to a fausse-braye or secondary rampart at North Weald. This arrangement would have allowed a more effective defence to have been conducted from these centres had the positions to the front of them been over run. Exceptions to this were to be found at Reigate, Fort Halstead and Pewley Hill. At Pewley Hill the rampart was surrounded by a ditch, deep, wide and revetted in concrete on both sides. Halstead had a less imposing ditch with concrete revetment to the nearly vertical escarp while the earthen counterscarp fell away at a 2/3 gradient. The ditch at Reigate was a simple, but deep, unrevetted V-shape at the base of the rampart.


In the main the centres were intended for infantry only, most being too small to accommodate armament. Of the larger centres, provision was made at North Weald for field guns to be placed on the rampart and supplied with ammunition from the magazines below, via shafts, the only instance of this in the London Mobilisation Centres. No emplacements existed, they were to be formed in the rampart on mobilisation. Casemates were provided to shelter the guns during a bombardment.


At Fort Halstead the design plan showed a number of small emplacements to be formed in the rampart, revetted in dry blockwork. As with North Weald, the type of weapon to be employed is not known but would appear to have been a mix of quick firers and machine guns. As with North Weald the weapons were intended to be movable and would have been sheltered in the nearby casemates until needed. Some small expense magazines were to be constructed in the rampart close to these emplacements.


As Pewley Hill was contemporary with Halstead and similar in form it is probable that similar provision was made there. As no plans have yet been located and the site built upon it has proved impossible to confirm this.


The final large centre, Reigate, appears to have been purely for infantry use, though there was room for howitzers to have been positioned inside on the parade, used in the indirect fire role. A supposition perhaps supported by subsequent addition of an earthen platform and traverse at the western end that may have been to accommodate artillery of some sort. The date of this alteration is not known, however, and it may have been done during either World War.


A further important function of the centres was to supply water. In some cases this relied upon rain water, collected, filtered and stored in large underground cisterns. This was supplemented or supplanted, at a few places by a supply laid on from a nearby water main.

To maintain the items stored in them, the centres had two resident caretakers who lived on site. Typically bungalows were provided for the caretakers to live in positioned along the approach road to the centres. In a few cases the accommodation was built into the gorge wall of the centre, from where the caretakers and their families would have been ejected on mobilisation. Loopholed steel shutters for external windows, steel external doors (also loopholed) and a flat reinforced concrete roof were provided for the accommodation in these cases.


When the scheme was first proposed the Volunteer Artillery were equipped with a mixture of 20pr & 40pr Armstrong Rifled Breech Loaders and 16pr Rifled Muzzle Loaders. These units were later re-equipped with 15pr and 4.7inch Breech Loaders, the ammunition for which required an increase in storage capacity at some locations. This was typically met by the construction of tool stores, simple brick store buildings with slate roofs just outside the centres concerned, to contain the tools. In turn, this released the bombproof casemates, formerly containing the tools, to hold the extra ammunition. There were to be 300 rounds of 4.7inch and 352 rounds of 15pr per gun stored in the centres. This, together with the quantity held by the units and at Woolwich gave a total of 500 rounds per gun.


There were exceptions to this however, at Reigate the tool store was situated within the Mobilisation Centre and had a flat concrete roof. At Denbies additional magazines were built alongside the existing ones under the rampart, obviating the need for a tool store. Westerham acquired a pair of caretakers cottages which would have freed the original bombproof accommodation in the gorge of the work for extra storage space. While at North Weald a pair of buildings, not unlike the tool stores seen elsewhere, were constructed to hold the additional shells and cartridges. Warley had a similar building added to increase the shell storage only.


With the decision to use civilian labour to construct the defences, a need arose to provide accommodation for the labours on site so as to maximise the time spent working on the defences. To this end tents and blankets were to be stored at some sites to provide temporary accommodation for them. The tents and blankets were generally housed in the tool stores though at North Weald, which did not have a tool store, a separate building was to have been provided.


The casemates and magazines were constructed from concrete though with varying forms of reinforcement to the roofs. One method was to fit Rolled Steel Joists, either set into the concrete or with brick arches sprung between them and overlaid with concrete. Other methods were to use "Old Railway Metals" placed side by side or brick vaults, to give strength to the concrete. Where there were casemates at the rear of the work these were usually of brick as were the internal walls of the magazines although concrete was used in some cases.


All centres had magazines to store the ammunition, most commonly a cartridge store and two shell stores in a block. The magazines were often set partially below ground level with the reinforced concrete roof mounded over with earth to provide additional protection. At Halstead this was further enhanced by a layer of flints set in the earth cover intended to detonate a shell before it contacted the magazine itself.


The shell and cartridge stores were normally accessed from the magazine passage which also contained the shifting lobby. Cartridges required special care in handling and personnel entering the cartridge store were required to change into special magazine clothing and shoes before entering. This took place in the shifting lobby, a section of the magazine passage outside the cartridge store and separated from the remainder of the passage by barriers. The magazine workers took off their boots and uniform outside these barriers, passed through, then put on magazine clothes and went about their duties. This ensured that no grit or metallic items, liable to cause sparks, could enter the cartridge store. Latterly this was of less importance as the 4.7inch and 15pr guns used brass cartridges that were much less susceptible to accidental ignition than the bag charges used with the earlier guns.


To provide safe illumination the magazines were surrounded by a lamp passage, entered from the magazine passage, that gave access to a number of lamp recesses. Lamps placed in these recesses in the walls shone through plate glass into the magazines. This arrangement prevented any contact between the explosive and the naked flame. Candles with triple wicks were used as the source of illumination. They were thought safer than oil lamps which, if knocked over, could spill oil which would ignite and cause a fire. The lamps were stored either in a lamp room or a recess in the magazine passage wall near the entrance to the magazine.


Normally there was a small chamber adjacent to the magazine, the fuse and tube store. This held the fuses for the shells and friction tubes used to fire the guns and, in some cases, small arms ammunition as well.


In order to prevent damp penetrating the magazines, the roofs were coated with bitumen and the walls surrounded by a layer of dry packing. Any moisture in this dry packing percolated downwards when it was carried away by agricultural pipe laid at the base of the packing. Both casemates and magazines were provided with ventilators ensuring a plentiful supply of fresh air. The amount of ventilation to suit conditions was the responsibility of the caretakers who adjusted shutters to regulate the air flow.


All centres were surrounded by fences that were one of two types, the Unclimbable or Dacoit fence, eight feet high and made from substantial steel angle irons, or simple railings 5 feet 6 inch high that would not have looked out of place around the local park. The latter also had two strands of barbed wire strung along the top. At Farningham and Reigate a shallow scrape in the glacis around the work would have been filled with barbed wire entanglements on mobilisation, providing additional protection to the sites. Entrance gates were usually of steel with loopholes for the defence of the entrance. Also seen were gates of the same style as the unclimbable fence. Uniquely, at Reigate both types of gate could be found.


The mobilisation centres were an early application of Crittal Steel Window Frames. These window frames were widely used throughout the mobilisation centres, although wooden window frames were also used in some places. Frames for the windows fitted with loopholed steel shutters had small opening panes that lined up with the loopholes in the shutters and the bolts that secured them.



The London Mobilisation Centres were built as part of a scheme to provide a viable defence for London at a time when confidence in the Royal Navy's ability to prevent an invasion was low. The fact that this relatively modest construction programme took some fourteen years to complete and ran out of money at least once would suggest that it was never taken entirely seriously. It was perhaps seen as a temporary and cheap expedient to pacify concern until the perceived weaknesses of the Royal Navy could be addressed. Despite the drawn out construction period, the London Defence Scheme could have functioned without the centres once the plans for the defence line to be constructed during the warning period were complete. It is tempting to conclude that the construction of the centres was used as an opportunity for the military to try out a variety of new designs to better assess their potential for future use. This would certainly explain the great variety in layout used throughout the thirteen fortified centres. The survival of most of the centres provides us with an interesting insight on fortification design during this period.


Sources Used

Documents at the Public Record Office from the WO32, WO33, WO78, ZHC and CAB 7, 16, 37 & 38 series.

Strategic Safeguard or Military Folly - Country Life, Brig Jock Hamilton-Baillie

Handbook for the London Defence Positions (Provisional) 1903 - Copy in UKFC Archive

Fort Halstead of the London Defence Positions - Brig Jock Hamilton-Baillie

Chatham & London The Changing Face of English Fortification - Post Medieval Archaeology, VTC Smith.

Looking for London's lost forts - Concrete, Feb 1982, Jack Barfoot

A Note on the Surrey Defence Works of the 1890's and their Construction - D W King

Notes on the History of the Old Fort and the London Defence Positions - L B Timmis M.S. Partridge Greenwood Press ISBN 0 313 26871 1



The authors are indebted to the various people who have helped with this article. Special thanks go to Tony Bailey at Farningham, Graham Roberts & Matthew Gimblet at Woldingham, Graham Hall & John Gordon at Westerham, Paul Scott and Brian Wilce at East Merstham, Hazel Price at Pewley Hill, Norman Jones, the former warden of Foster Down, The National Trust, owners of Box Hill and Surrey County Council, owners of Henley Grove for their support in allowing access to these sites. And to David Moore for suggesting it and producing it on his superior Microsoft free, non-Intel, computer.

Thanks also to Ann Bennett, Peter Cobb, Carole Owen, Jock Hamilton-Baillie & Victor Smith for their assistance.


Plan and gazeteer of the London Mobilisation Centres