8
‘Early Stone Age’ was Churchill’s description in 1939 of the aircraft-warning system over land. He was then visiting Bawdsey to see the progress of radar. The great towers on the coast could look far out to sea, but behind them over the countryside and towns they were almost blind.
Special constables who were members of the Observer Corps spent many hours of their spare time watching from hill-tops and plotting in stuffy rooms. They would doubtless have been incensed at Churchill’s remark, but, Stone Age or not, their work was vital. Where radar ended at the coast the whole weight of responsibility for accurate records of aircraft movements lay with the Observer Corps and its telephone network.
In common with the rest of the air defence system painstakingly built up between the wars, the Observer Corps was proved in the Battle of Britain. A year later, in April 1941, the prefix ‘Royal’ was granted in recognition of the Corps’ services during the fateful period from July to October 1940.
The idea of visual and aural observation systems was not new. Most countries, including Germany, developed them during and after the First World War. Only in Britain, however, was a layout developed and perfected which could provide accurate continuous tracks and recognition of aircraft types. The German aircraft-reporting service, Flugmeldienst, which was a regular uniformed formation, even in 1944 was plotting only rough bearings and approximate heights. It did not report types or numbers of aircraft. In contrast the volunteer Observer Corps had been able by the Battle of Britain four years earlier to indicate the position of aircraft on a two km. map square, with a good height estimate, the type and strength. Cooperation between two posts provided corrected heights.
The success of the Observer Corps system is accounted for almost entirely by the enthusiasm of volunteers. It was like a large club with an intimate atmosphere and a marked dislike for the more unpleasant feature of military discipline.
The Observer Corps had its roots in World War I when the Admiralty arranged for the police to report aircraft heard or seen within sixty miles of London. In 1915 this scheme was extended to cover the whole of England and Wales. The Admiralty received telegrams and telephone calls from the police and passed relevant information to the War Office. Warnings were issued to railways and Scotland Yard only. Appalling congestion of telephone lines resulted, and in 1916 the War Office took over. Troops were used instead of police, but they proved inefficient and the responsibility of reporting returned to the police.
In the autumn of 1917 Major General E. B. Ashmore assumed command of the London air defences. Dissatisfied with delays and overlapping, he initiated a new system early in 1918 in which all types of defence units reported through various centres to an operations table at his headquarters. The costly telephone network was not completed until May 19th, 1918, after which date the Gothas and Zeppelins failed to oblige with their presence.
After the armistice the reporting system was swept away and its relics pigeon-holed among the dusty files at the War Office.
On the revival of a semblance of air defence in 1924 it was clear that large areas would lack completely any form of aircraft intelligence. A sub-committee of the Committee of Imperial Defence was therefore set up under Major General C. F. Romer to study the question. One of the members was Ashmore, who was able to give the benefit of his practical experience during the war.
The committee accepted the principle that ‘the civil population will be so vitally affected by air attacks that the responsibility for observation and warning cannot be considered exclusively military’.
In August and September 1924 Ashmore organised the first observation experiments. Nine posts were set up in the area between the Romney Marshes and Ton-bridge. The village post office at Cranbrook in Kent was used as a control centre. Excellent tracking was obtained by day and night and Ashmore was empowered to organise a system in two zones covering the whole of Kent and Sussex. Each zone consisted of a network of Observer posts connected by direct telephone line to an Observer centre. The centres were linked to the air defence headquarters. All personnel were recruited as unpaid special constables and enrolled by the chief constables of counties and boroughs.
The first two ‘groups’ had headquarters at Maidstone, Kent, and Horsham, Sussex. Such was the speed at which Ashmore worked that by June 1925 air exercises were being held using the two centres. With three R.A.F. squadrons the coast-watching organisation and part of fighting area headquarters co-operating, the exercises proved very successful.
On the basis of the exercise reports the Home Office and the War Office sanctioned the new Observer Corps. Ashmore set up two further zones, in Hampshire and the eastern counties. By the end of 1925 he and Colonel Day, his signals officer, had created four group headquarters and 100 posts.
The basic organisation of the Observer Corps which later operated in the Battle of Britain was laid down by Ashmore in this period. He obtained direct G.P.O. lines for the posts and centres and introduced the gridded operations room table on which coloured counters were placed for plotting. The counters were exchanged for others of a different colour every five minutes to avoid confusion with stale information. The plotters at the table were each connected to three posts in a ‘cluster’ and a ‘teller’ looked down from a precarious box on high to report to Air Defence of Great Britain the tracks as they appeared. This system was to become standard throughout the R.A.F. defence network.
Observers at the posts were provided with an instrument which consisted of a flat circular map table, spindly tripod legs and on top what appeared to be a pantograph stood on end. This plotting apparatus, produced by the War Office at minimum cost, became familiarly known as ‘Heath Robinson’.
As the Observer Corps expanded it became evident that the Air Ministry was the authority most competent to control it. Accordingly in January 1929 the R.A.F. took over from the War Office and a Command appointment was created. This was to be filled by a retired R.A.F. officer of air commodore or group captain rank. The first commandant of the Corps, Air Commodore Masterman, was appointed on March 1st, 1929, and retained the position until 1936.
The four existing Observer groups were attached to four of the fighting area stations: No. 1 Group, Maidstone, to Biggin Hill; No. 2 Group, Horsham, to Kenley; No. 3 Group, Winchester, to Tangmere; and No. 18 Group, Colchester, to North Weald.
The Romer Committee envisaged a further fourteen groups but by mid-1931 only the original four groups existed. It was not until May 1931 that permission was given for the formation of a fifth. No. 17, with its centre at Watford. No more were organised until 1933. In the intervening years the original groups soldiered on, participating in various air exercises. There was little to show the existence of an Observer post except for a pair of telegraph wires ending, for no apparent reason, in some out-of-the-way spot, and the last telegraph pole having a small wooden box on it usually filled with earwigs.
When the R.A.F. required the services of its ‘eyes and ears’ a man would arrive with a bulky box. From this he produced a length of cable and inserted one end into the box on the pole. The tripod was then set up and an extraordinary assortment of men in plus fours, gumboots or perhaps spats proceeded to gaze skywards. One turned the upended pantograph hopefully in the direction of a passing aircraft, another spoke into an antiquated army head and breast telephone set. The Observer Corps was a source of bewilderment to the passing public and high amusement to inquisitive small boys, but it worked.
Gradually the effects of German rearmament began to tell, and a sub-committee under Air Commodore Boyd recommended in January 1935 that eleven new groups should be formed by March 1939, and the Corps should be divided into two areas, north and south.
By the summer of 1935 No. 16 Group, Norfolk and Suffolk, had been added. Groups Nos. 4, 11, 12 and 15 were formed in Oxfordshire, Lincolnshire, Bedfordshire and Cambridgeshire in time for the air exercises of 1936.
Meanwhile in 1935 exercises were planned by the Home Office for the following year with full-scale blackout restrictions and air raid warnings. It was then realised that a raid warning system could only be developed in areas where the Observer Corps operated. Since it was impossible to declare areas immune to attack the only course was to provide complete coverage of the country with the reporting system. This was a recommendation of the Boyd sub-committee.
In 1936 Air Commodore Masterman retired. His place as commandant was taken by Air Commodore Warrington-Morris, who was to guide the Corps in its greatest expansion period and through three years of war. As the pace of rearmament quickened, so did the creation of new Observer groups. In 1937 it was decided to extend the system to the north and west of England and to Scotland. The country was divided into five areas. Each area was administered by a small staff of retired officers but directly controlled from the Corps headquarters, this being removed from Uxbridge to the new Fighter Command headquarters at Stanmore, Middlesex, where it has remained ever since.
The expansion brought many headaches to the small staff of the Corps. Suitable sites for new posts were being surveyed and negotiated throughout the year and these had to be linked with telephone lines to new centres. This placed a massive burden on the G.P.O., while enrolling volunteers, and the provision of even the standard meagre amount of equipment placed a great strain on the Corps officers.
The Munich crisis came during the expansion and on September 26th, 1938, the Observer Corps was called out for the first time as a fully fledged organisation. The system passed the test although faults came to light, particularly in communications, which provided valuable pointers for the future. When by October 1st ‘peace in our time’ was the slogan the Corps telephone network was restored to normal and the crews were disbanded.
Less than a year later the Corps was out in force for the annual air exercises of August 9th–11th, 1939. For the first time the full warning system was operated. The Corps was given information provided by the Chain Home radar stations, although the rank and file had no inkling of how this was obtained.
Less than a fortnight later the Corps was once more on the alert, this time in earnest. War was inevitable.
On August 24th, 1939, while holiday-makers sunned themselves and one newspaper proclaimed there would be no war, the Observer Corps manned its posts and centres and began a watch on the skies which was to continue unbroken for six long years.
When it was mobilised the Corps consisted of thirty-two centres, over 1,000 posts and about 30,000 observers. There was a nucleus of paid full-time officers and observers but the great majority fitted in part-time duties with their normal work.
The centre table of No. 17 Group Observer Corps as it appeared during the Battle of Britain. On the right the plaque shows Raid 494 with six hostiles at 15,000 feet, while alongside it are two fighters from Hornchurch climbing through 5,000 feet to intercept. T.8 near the centre is an unidentified sound plot. At the top of the table 50 hostiles are being engaged by 30 fighters from North Weald. On other parts of the table are various friendly aircraft including trainers. Squares 68, 78 etc. have 10 km. sides and are subdivided into 2 km. squares
From August 24th complete administration including pay and recruiting passed from the Police to the Air Ministry. Observers relinquished their status as special constables. The Corps volunteers objected strongly to being paid and in the commandant’s circular for October 5th, 1939, it was noted that ‘a member is not bound to claim the hourly fate if he does not wish to do so’.
The Corps layout in September 1939 remained fundamentally the same for the Battle of Britain a year later, but in the intervening months many new posts were initiated and others re-sited for better observation.
Four large gaps existed in the Observer coverage: the whole of north-west Scotland, a large part of southwest Scotland, the whole of west Wales and all Cornwall. These gaps were not completely filled until after 1940.
The Corps structure revolved round the centre at group headquarters where the crews worked on a shift basis. Here in a small room a plotting table was set up around which sat twelve plotters wearing head and breast telephone sets connected to clusters of two or three posts. A floor supervisor checked the state of the table and the continuity of tracking. Behind him slightly raised on a wooden dais sat the tellers who passed on information to the group and sector operations rooms and to adjacent Observer centres. One centre would provide information for up to six sectors, as in the case of Bromley, Kent, which was linked to Biggin Hill, Hornchurch, North Weald, Kenley, Northolt and Tangmere.
At the end of the line of tellers perched on a wooden box was the recorder who pencilled tracks on grid paper. Two other people of particular importance were the duty controller at the group centre and the Observer Corps liaison officer at Fighter Group headquarters. The latter formed the link between the R.A.F. and the Observer Corps network.
Around the group centre radiated the posts of which there were usually thirty to thirty-four. Each post consisted of some sort of weather protective frame either of wood, sandbags or even railway sleepers. A standard pattern hut was issued, but hard to acquire. The only items common to all posts were the instrument for estimating the position of aircraft, the telephone, binoculars, raincoats, gumboots, a log book and some means of making tea. There is no record of any unit of the Observer Corps being so backward as to be unable to brew tea at frequent intervals. Uniforms were not issued, the only distinguishing marks worn by post observers being armbands and steel helmets, if they were lucky enough to obtain them.
The post might number between fourteen and twenty observers with a head observer in control. The instrument itself was of improved form compared with the ‘Heath Robinson’ of the ’twenties. Of all-steel construction, it had a built-in height bar and geared sighting arm, and a device for correcting height estimates when two posts plotted the same aircraft.
The instrument was mounted in the centre of a gridded circular map of ten miles radius on which the five-mile circles of nearby posts were shown. When an aircraft was sighted the observer with the instrument estimated the height and set the bar accordingly. By viewing the aircraft in a ring sight he moved a pointer to a particular 2 km. square of the gridded map. His companion then passed the position indicated, by land-line, to the centre in a standard form; for example, ‘B.2 calling, three planes seen 6153 flying north, height 8,000 feet.’
The plotter at the centre placed an arrowed marker on the appropriate square using the colour shown on the clock for the five-minute period, red, yellow, or blue. The marker pointed in the direction of flight. Rectangular counters were added to show eight on blue for the height of 8,000 feet, three on red for the strength, and white on a black letter B to indicate ‘bomber’. Other counters denoted variations of this. Enemy raids were shown as numbers allocated by Fighter Command from radar plots or, if initiated by the Observer Corps, with a prefix letter of the group of origin; for example, ‘C’ for Colchester.
In sound plotting posts gave only a bearing and the direction of flight. The bearing was in the form of a numbered square on a five-mile sound circle on the charts. The centre plotter on receiving this laid a trumpet-shaped counter on the post’s circle on the table pointing towards the post itself. When a plot came in from another post, a similar procedure was carried out. At the intersection of the two angles a counter called a ‘Halma man’ was laid, and a track begun. Special priority was given for low-flying enemy aircraft. The post plots were prefixed by the words ‘Low raid urgent’.
This simple basic system for reporting and plotting could be modified to meet different situations. With practice it provided the fastest flow of accurate information obtainable. Reports of plots from the posts to the Observer Corps network often reached over one million in twenty-four hours. A plot obtained by even the most remote post could be transmitted to Fighter Command in less than forty seconds. This was a remarkable achievement.
There was little practice in aircraft recognition in the three services before the war. Its neglect by succeeding R.A.F. directors general of training was to be the cause of many casualties for the first two years. Even Fighter Command’s recognition knowledge was scant. The repeated identification of non-existent Heinkel 113s during the summer of 1940 was proof of this.
During the early months of the war ‘enemy’ tracks appeared frequently on the operations tables throughout the country. Each was the subject of investigation and analysis.
On September 6th, during the ‘Battle of Barking Creek’, British fighters attacked one another and plots of hostile aircraft were shown at the Bromley centre. The controller, puzzled because no raids developed from the seaward plots shown, sought information from the post reporting hostile aircraft. His comments later read as follows: ‘The observer reported a definitely overhead as a bomber. I was doubtful as there were fighter tracks in the vicinity and asked the observer how he knew, and he said: “Because it is black and white underneath and it is being fired at.” A nearby post came in and said that they could have told us it was a fighter, but he was not given a chance to report.’
Gradually the Observer Corps grew more proficient at recognition but the R.A.F.’s skill remained comparatively poor in this respect. Among the dozens of tragedies in 1940 through inability to identify aircraft three are worthy of mention.
A Hurricane pilot shot down an unarmed Hudson packed with Australian aircrew. He was convinced the aircraft was a Dornier 17. Two Blenheims mistaken for Ju 88s were chased halfway across the Channel by a Polish Hurricane squadron and shot down in flames. An instructor and pupil flying in a Hawker Hector over a peaceful area passed a strange low-wing monoplane. The stranger shot them down and machine-gunned them after they had taken to their parachutes, killing the pupil and mortally wounding the instructor. Before he died the instructor said he assumed the plane came from a nearby experimental airfield. In fact it was an Me 110.
It was formerly never the Corps’ duty to identify aircraft types, machines being classified only as ‘friendly fighters’, ‘bombers’, ‘hostile’ and ‘unidentified’. According to the small booklet Instructions for Observer Posts which was the only post training manual issued, all bombers were to be regarded as hostile. This scheme worked quite well in peacetime during exercises, but was useless in war.
Many members of the Observer Corps, being enthusiasts, studied cigarette cards, and purchased technical journals such as Aeroplane and Flight. In 1935 the Corps was issued with an official service silhouette manual which was at that period usually out of date and often very inaccurate.
Shortly after September 1939 officialdom realised that the Corps could identify aircraft as types. Already keen posts were reporting in this fashion. The supply of recognition material began to improve slightly, although in the autumn of 1939 No. 29 Group was moved to invent recognition doggerels, one of which stated:
There is little to relate
Of the Junkers 88,
It’s small.
That’s all.
When reprinted in an official Corps document a footnote was added to the effect that this was the ‘only information available on the Junkers 88’.
It was left to the members of the Corps to conduct their own schemes of training and proficiency tests.
On December 9th, 1939, a party of forty observers met in the Corona Café, Guildford, to form ‘a study circle, or club, to provide facilities for members of the Corps to make themselves proficient in the practice of detecting, plotting and identifying aircraft’. The organiser was Mr. H. J. Lowings. Mr. Peter Masefield, then of The Aeroplane staff, delivered a lecture on ‘The Recognition of Aircraft’.
Official Air Ministry silhouettes of 1940 showing the Hurricane and Spitfire. By this period recognition material was at last beginning to improve, the pre-war material being hardly identifiable as any type
The study circle became known as the ‘Hearkers Club School of Instruction’. It was this kind of enterprise and enthusiasm which enabled the Corps with little official help to separate friend from foe in the Battle of Britain and thus greatly simplify the task of Fighter Command. Ultimately the Hearkers Club became nation-wide and formed the basis for service recognition training.
The main enemy of the Corps in its first eight months of war was not the Luftwaffe but boredom and an appalling winter. A few posts saw German aircraft, particularly over Scotland, but most watched and waited for hour after hour. They stood in the sun, the rain, and then the deep snow and hoar frost at the turn of the year when some posts were snowed up for two days awaiting their relief crews.
The time was not wasted, however. Gaps in coverage were being filled, telephone communications improved, and frequent exercises greatly accelerated and streamlined the plotting at posts and centres. The Corps had its own methods of maintaining relations between units apart from the normal ‘Operations Instructions’. One of these was a fortnightly circular issued personally from Bentley Priory by the commandant, Air Commodore Warrington-Morris. This duplicated manuscript was hardly in keeping with the normal turgid and wordy documents pouring out of the headquarters of the services, but well laced with broad humour it typified the volunteer atmosphere of the Corps.
In February 1940 the commandant’s circular noted that there was a considerable increase in enemy air activity over the North Sea and that a ship had been attacked in the Channel.
The end of the phoney war was approaching but this was not apparent to the centre crews and post observers who struggled to speed up plotting and reporting and to remove the bugbear of the time lag between sighting an aircraft and its notification on the Fighter Group operations table. A typical report of the period ran:
A daylight exercise carried out by No. 12 Fighter Group on March 1st was disappointing: tracks of the aircraft were not continuous and several were missed altogether. Where large numbers of training aircraft are flying at a low altitude it is difficult for posts’ crews to pick up and report aircraft flying at a high altitude but it is a problem to be faced and one that calls for a high degree of co-operation between centre and posts’ crews. In addition the handing over of a track from one centre to another is a matter of the greatest importance. The exercise was repeated on March 5th with much better results but 100 per cent efficiency was not attained.
Inside an Observer Corps Operations Room in 1940. This is 17 Group Watford. Around the table are the plotters receiving reports from the posts. A table supervisor leans across to check a plot. At the dais on the right are the liaison officer, the assistant duty controller and the duty controller, while perched on the dais at the left are the tellers
The Corps found by April 1940 that it was reporting many items other than straight plots. Special attention was given to British aircraft lost or in difficulties. Blackout infringements and other suspicious incidents were notified and coastal posts saved lives by reporting promptly aircraft down in the sea. Some posts near sector stations were equipped with paraffin flares to guide night fighters back to their bases, thereby sometimes incurring the wrath of the local populace for breaking the blackout.
Plotting standards on posts varied according to the literacy, eyesight and hearing of the members but surprises could still be sprung on the R.A.F. At one post a new type of aircraft was reported which was still secret and of which no silhouettes or description had been issued. Inquiries elicited the laconic reply ‘We are always up to date.’ It was later explained that one of the post’s crew was working on the aircraft at a nearby factory.
When the Dunkirk evacuation came at the end of May 1940 the Corps found itself in the front line overnight with the south coast groups facing an enemy rapidly absorbing the whole north coast of France. Urgent instructions went out to posts to protect their weather shelters with earth revetments and to watch for paratroops, troop-carrying aircraft and gliders. Rifles and overalls were issued to posts in the danger areas although the outlook for observers defending their posts in the event of invasion was far from bright, despite promised assistance from the Local Defence Volunteers.
The brief for the Corps was short and to the point. ‘Every centre and every post must be continuously manned as long as humanly possible.’
Posts came under fire for the first time in late June when enemy air activity was increasing. A bomb dropping within fifty yards of one was unnoticed by the observers who were busy plotting. At another, where a bomb dropped closer, the Corps commandant noted later that he was asked ‘to supply a new pair of trousers’.
German aircraft cruised over England and Scotland throughout July sometimes by day but mainly by night probing, training and dropping bombs and mines. As the month advanced the attacks were concentrated on Channel shipping and the coastal groups of Yeovil, Winchester, Horsham and Maidstone were witnesses to many fierce actions as the convoys fought their way through.
On the 13th August the Luftwaffe officially opened its long-awaited offensive against England and for the next three months the Observer Corps’ years of practising and exercising were put to their most stringent test.
Observer Corps post 17/K.1 in 1940. This post was situated on the top of the Senate House, London University. One Observer is following an aircraft using the post instrument (complete with telescope) while the other Observer reports to centre with a head and breast telephone set. The post is surrounded with sandbags and the numbers hung round the walls indicate 2 km. squares on the British Grid System
The volume of information pouring in during those summer days from a comparatively small area was enormous. All of it had to be quickly plotted and analysed. There were scattered raids throughout the length and breadth of the land, but the main daylight concentration was over the areas of the Observer groups within No. 11 Fighter Group R.A.F., namely, No. 1 Maidstone, No. 2 Horsham, No. 3 Winchester, No. 17 Watford, No. 18 Colchester, and No. 19 Bromley.
In these groups, day in day out, the posts queued on the telephone lines to give their plots and the centre staffs worked like machines to convert them into plaques and arrows and pass the information to the Fighter Group headquarters.
With such concentrated activity there were bound to be problems. Some posts became ‘saturated’ with aircraft overhead and could only give approximate numbers, others found themselves dealing simultaneously with raiders at tree-top height and 28,000 feet, often while under machine-gun or bomber attack.
Two difficulties were never really overcome. The first concerned persistent unidentified tracks appearing on the Fighter Group operations table and originating in Observer Corps groups. Dowding drew attention to the fact that these must be a lost raid freshly plotted, a raid missed by radar, or a friendly aircraft. The Observer groups without proof by recognition (particularly on cloudy days) were most reluctant to identify a track as friendly because it would then be removed from the operations room table and a hostile machine might get through to its target. If the group labelled it hostile a friendly aircraft might be attacked by the defences.
The second problem concerned height. All Observer visual plots were based on estimation of height before the post instrument could be set to give a map position. Thus wrong estimates not only gave an incorrect altitude for fighters to intercept but misplaced the track on the map. Varying estimates tended to make a track zig-zag on the plotting table and altered its apparent speed.
The estimation of height from the ground is exceptionally difficult even with long practice. At the height of the battle posts had insufficient time to correct heights by comparison with the instrument readings of neighbouring posts.
A page from the Bromley Observer Corps Centre log book for August 28th, 1940
Radar in 1940 often gave height incorrectly, sometimes by several thousand feet. This defect in the mechanical and the visual systems was the primary cause of fighters directed to the enemy finding themselves underneath an opposing formation instead of on a level with it or above.
Many pilots complained bitterly of these inaccuracies but it was miraculous that they were not more frequent or that the system, strained to the utmost, could work at all.
