The system

‘The war will be won by science thoughtfully applied to operational requirements.’ So wrote Dowding to the head of operational research at Fighter Command in November 1940. These few words summed up the essence of the R.A.F.’s survival and victory in the Battle of Britain.

Dowding realised from the inauguration of Fighter Command in 1936 that the country could never be defended against air attack unless the fighter forces could operate as part of an intricate but reliable system. This would have to give continuous warning and control and conserve the forces in combat.

Piece by piece the giant jigsaw puzzle was assembled, each section interlocking exactly with the next. Warning of attack came first from radar. From the coast it was the responsibility of the Observer Corps and the information was passed to Fighter Command and the fighter groups. From there the orders were relayed to the fighting sectors, where with H.F. radio, ‘Pip-Squeak’ and high-frequency direction finding the controllers could direct the Spitfires and Hurricanes to the attack at the right place and time and guide them safely back to base.

Such ideas are now commonplace but in 1940 they represented an astounding co-ordination of design and organisation which was without parallel in the world. Controlled scientific air defence was unknown in Germany at this time. The accent in the Luftwaffe was always on offence.

Without years of similar experience in building up such a network the Luftwaffe could not anticipate the opposition it would afford nor for a very long time could the full secrets of how it worked be unravelled. The air forces of Poland, Norway, Belgium, Holland and France possessed no worth-while air defence system. Accordingly they were smashed on the ground or shot out of the sky in a matter of days. After these victories the German Air Force might be considered justified in believing the task of demolishing the R.A.F. as well within its capabilities.

It was not until the Luftwaffe radio monitoring service and the German Post Office set up their listening stations on the coast of France in July 1940 that the Luftwaffe realised it was up against something new and of vital importance. First the operators discovered that the ether on the twelve-metre band was alive with signals radiating out across the Channel from the tall and seemingly silent radar masts along the English coast.

The second shock came as the Channel convoy battles developed. British voices could be heard on H.F. accurately directing formations of fighters towards unseen German raiders. The air was full of voices, calmly and systematically placing fighters here and there and guiding others back to base. It dawned on the listeners that this was part of a complex and smooth-running organisation of great size.

In Britain from 1937 onwards no effort had been spared by hard work and trial and error to integrate all the facets of R.A.F. defence. Each succeeding air exercise, so often criticised in the Press, solved one more problem of warning or communications so that by the summer of 1940 the layout was operationally streamlined.

The key to the system of control lay in the fact that from commander-in-chief down to sector controller the display of information was the same and changes were made simultaneously throughout. It was this standardisation and the use of synchronised colour clocks which enabled Fighter Command to bring forces to bear when and where they were necessary and to avoid the waste of standing patrols. An exceptional degree of flexibility was possible. This allowed for the rapid transfer of reinforcements from one group to another and quick appreciation of threats by adjoining groups.

All operations rooms, small and large, were of a similar pattern with the controller and his aides on a raised platform. Below were airmen and W.A.A.F. plotters with their headphones, working day and night moving counters with their long ‘rakes’ for all the world like croupiers at some weird casino.

Behind all this lay the arteries and veins which fed the heart and limbs, the telephone lines. Until 1938 the R.A.F.’s telephone network was little more than a skeleton with a massive switching of public lines for defence exercises.

Sir Philip Joubert de la Ferté, who took command of the then Fighting Area in 1934, writing of the air exercises of that year, records:

In theory we were supposed to have three lines to each sector: an ‘A’ line for passing orders, a ‘B’ line on which to receive the acknowledgement of the orders sent, and an ‘I’ line for intelligence reports, combat reports and any information regarding the battle. During one hectic half-hour when raids were coming in fast, first the ‘A’ line, then the ‘B’ line and finally the ‘I’ line went dead and I was left without any means of issuing orders to my fighters.


W.A.A.F. plotters at the table in the Duxford sector Operations Room. On the right can be seen the croupier’s rakes for moving raid plaques placed on the gridded map. The name Hornchurch and part of the coast are just visible. On the left are racks containing the various discs and plaques used on the ops table

Steady improvements were made after 1934. Permanent lines were installed to the sectors but only a fraction of the communications necessary were available when Munich came. The General Post Office was concerned with planning for the R.A.F. from 1935 with the ‘Air Defence Group’ but the work was mainly concerned with calculators and other equipment for the radar stations.

In 1938 a complete review was made of existing arrangements for the provision of emergency circuits for all the services. By August 1939 switching was available for some 500 long-distance emergency circuits and a much greater number of similar circuits of under twenty-five miles radius. A large proportion of these were required for the R.A.F. and at the end of August all were turned over to military lines. Within months many switched lines had been converted into permanent private service lines.

To meet a flood of urgent requests for lines, repairs and maintenance on the military communications system the G.P.O. inaugurated the Defence Telecommunications Control (D.T.C.) organisation with regional branches throughout the country.

As well as telephone circuits the services had a heavy requirement for reliable telegraph circuits. The Post Office suggested a new network partially independent of the civil telegraph service, and with voice frequency equipment at the service establishments. On July 14th, 1938, the chiefs of staff of the three services, telephone engineers and six representatives from Standard Telephones and Cables Ltd. met to discuss the vast project.

Treasury authority was given for the scheme, which became known as the Defence Teleprinter Network (D.T.N.). The Post Office and Standards installed for the R.A.F. a teleprinter network serving Fighter, Bomber, Coastal and Maintenance commands with a mass of terminal apparatus. The production and installation of this put a heavy burden on the Post Office engineering department and on the manufacturers.

The first multi-channel telegraph system of D.T.N, was opened on March 31st, 1939, between Uxbridge No. 1 (No. 11 Group) and Faraday Building, London. On April 4th Uxbridge No. 1 was linked with Stanmore No. 1 at Fighter Command Headquarters. From this time on terminals were installed at an increasing rate to link the widely spaced segments of fighter defence. In the summer of 1940 the D.T.N, was to be flooded with messages, combat reports, intelligence reports, pilot and aircraft replacement requirements, damage assessments and a host of others

A particular headache of the G.P.O. was the maintenance of communications under air attack. The problems of field repairs came under the Post Office War Group headed by Mr. H. R. Harbottle at the engineer-in-chief’s office. The War Group became the focal point for the activities of the Defence Telecommunications Control Organisation.

Throughout the Battle of Britain, despite acute manpower problems, the Post Office managed to keep communications going at radar stations, Observer Corps groups, R.A.F. command, group and sector operations rooms and airfields. Bombing caused tremendous damage in the summer of 1940 to radar stations and airfields. Some sector operations rooms were transferred to other buildings but somehow the civilians from the Post Office and R.A.F. signals officers managed to ensure that Fighter Command’s system continued to function.

Fighter Command was organised into four fighter groups, Nos. 10, 11, 12 and 13. For tactical control purposes each group was sub-divided geographically into sectors. Each sector contained a main fighter station and sector headquarters with its operations room and direction-finding stations linked to it. In addition one or more satellite airfields with squadrons based on them were controlled by a sector. The number varied to operational and dispersal requirements.

No. 11 Fighter Group covering south-east England bore the brunt of the attacks while the other groups defended their own areas. Where necessary they reinforced No. 11 Group, and supplied fresh squadrons to replace those worn out or depleted by fighting.

At the headquarters of the command and each group and sector was an operations room differing in size and complexity according to its scope. All, however, were provided for the one main purpose of securing the utmost speed in the issue and transmission of orders by landline or radio.

At Bentley Priory, near Stanmore, Middlesex, lay the heart of the system, the Fighter Command operations room. This was the only room where aircraft tracks over the whole of Britain and the sea approaches were displayed. From 1925 to 1936 the Air Defence of Great Britain had its operations room in a wooden hut opposite Hillingdon House, Uxbridge, Middlesex. It was clear that this was of no use for controlling Fighter Command. In 1936 the princely sum of £ 500 was allocated for an experimental operations room in the ballroom at Bentley Priory. The deputy director of plans at the Air Ministry in desperation asked in June for a permanent arrangement and added: ‘We cannot waste any more time, we have had twenty years to decide.’

In the early days of radar the operations room was situated in the ballroom with a rudimentary filter room one floor below in the basement where the bar now stands. To shorten the circuitous route from filter to operations rooms Dowding ordered a hole to be knocked in the walls so that the steps led straight from one room to another.

The Priory was extremely vulnerable. One well-aimed bomb could have wrecked the radar plotting centre and the structure of command. Accordingly the Air Ministry ordained that Fighter Command and Nos. 11 and 12 Groups should have concrete underground operations rooms. The work at Bentley Priory was not to exceed £ 4,500 in cost! Inexplicably the R.A.F. was loath to give protection to its vitals. It seemed to have a marked aversion to solid safe centres below ground and it was not until March 9th, 1940, that the Fighter Command operations and filter rooms left the Priory and went down to their concrete basement.

The command and the two groups were the only well-protected sites until the end of 1940. The radar stations, the Observer centres and the sector operations rooms remained throughout most of the Battle of Britain naked and above ground and often suffered accordingly.

In one room of the concrete bunker at Bentley Priory was the filter centre where all radar plots of position, strength, height and direction were received from the C.H. and C.H.L. stations. Each radar station was represented by a filter officer at a crescent-shaped filter table. On this was painted the outline of the British Isles, the Channel, North Sea and a large part of northern France. The filter officers checked all information by cross-reference and I.F.F. The filtered plots were then passed direct to the command operations room next door and to the fighter groups by landline.

The identification of hostile aircraft on radar plots by the use of I.F.F. was not always reliable. Unidentified planes reported by radar or observers were treated as hostile until identified. There was no alternative to this method but it meant that the table, particularly in cloudy weather, carried a crop of hostile and unidentified or ‘X’ plaques which were the nightmare of group and sector controllers.

Each enemy raid picked up by radar was allotted a raid number such as ‘hostile 1’ or ‘hostile 2’. This was supposed to follow it on the plots through its flight over Britain but duplication and confusion often occurred when large numbers of enemy aircraft were involved and tracks were being handed on to the Observer Corps overland.

The command operations room received its Observer Corps information through the fighter groups which disseminated it throughout the system. Dowding and his senior officers thus had a complete picture of the defence position. With it was given full details of squadron availability. During July and August 1940 all information was shown on the main table but by September this was becoming so congested that a slotted blackboard known as the totalisator or tote was erected.

The tote recorded all details of enemy raids and fighters sent to intercept. This left the table map clear except for the raid numbers and symbols for the airborne interceptor squadrons.

In addition to the commander-in-chief and his staff Stanmore operations room housed the commander-in-chief of the anti-aircraft defences, the Observer Corps commandant or their representatives, liaison officers from Bomber and Coastal commands, the Admiralty and an officer from the Ministry of Home Security. Each had his seat on the dais and telephone lines to his organisation.

The air raid warning system was operated from Stanmore through special trunk exchanges and direct telephone lines. Dowding also exercised general control over the A.A. guns and searchlights through the commander-in-chief of Anti-Aircraft Command and he was responsible for the balloon barrage through the fighter groups.

The operations room at No. 11 Group at Uxbridge was similar to that at the command but with a map showing only the group’s area and its adjoining land and water. The information displayed was similar to that at Stanmore except that the area represented was restricted. The tote board showed only the group’s squadrons and any units on loan from 10 or 12 Group dealing with German raids in the area.

Park, the group commander, received his filtered radar information from Stanmore and his visual and aural plots direct from the tellers in the Observer groups in his area. He directed sectors to deal with raids as the plaques appeared on the map table.

The final links in the chain were the sectors. These directly controlled the fighter squadrons. Sectors were lettered A to Y from Dorset round the coast and upwards to Edinbugh and Glasgow. Sector operations rooms were usually on or adjacent to the main airfield. They Were housed in buildings varying from concrete emplacements to flimsy wooden huts. The emergency stand-bys were even more peculiar, one being housed in a butcher’s shop and another sandwiched between a fish frier and a public house.

Sector operations rooms consisted of two separate units. In the direction-finding room the positions of fighter aircraft were obtained from ‘Pip-Squeak’ bearings and the radio direction-finding stations. The second unit was sector ops which resembled group operations in miniature. The main floor was occupied by the general situation map around which sat about half a dozen plotters. The tracks, raid plaques and other indicators were placed in position according to filtered radar information received from Bentley Priory and from plots ‘told on’ from adjacent Observer Corps centres. In the centre of a raised dais facing the map table sat the controller flanked by ‘Ops A’ and ‘Ops B’. ‘Ops A’ was an airman or W.A.A.F. who took down instructions direct from the group indicating the serial number of the operation, squadron or section strength to be employed and the number of the raid to be intercepted. This information was written on a form ‘A’ and handed to the controller for action. ‘Ops B’, usually a flight lieutenant, at the controller’s right hand manned the communications keyboard while ‘Ops B1’, a sergeant, controlled the master switchboard with all incoming and outgoing lines including those to the airfield and its satellites. Also on the dais was the local gun-control officer and a man responsible for liaison with the Observer Corps.

Two deputy controllers sat at desks in front of the dais. Each was accompanied by a dead reckoning navigator. They received D/F-‘Pip-Squeak’ information on the fighter’s position, and with tracing paper, rulers, compass rose and pencil worked out the triangulations to intercept the raid indicated by the general situation map.

On the wall opposite the controller hung the five-minute colour-change clock, the weather board and the all-important ‘state’ panels. These last were the sector equivalent to the command and group totes. They consisted of four-foot high boxes, six inches wide and three inches deep, on which were printed the various states of readiness of the squadrons in the sector such as ‘Released’ and ‘Thirty minutes readiness’. One box was allocated to a squadron and under each readiness category were six lamps coloured red, yellow, white, blue, green and black which indicated the flying sections concerned. Thus at a glance the controller could tell the exact state of the units under his jurisdiction.

On receipt of an order number from group the controller would order a selected unit to ‘scramble’, using its code name for the day. Brief information of the area to be covered and operating height would be given. When hostile aircraft came into the area, perhaps ten minutes later, on receipt of a further order from group, the controller would direct the fighters to the raid using the triangulations worked out at the deputy controller’s tables.

The sector controller retained executive authority over the aircraft he despatched until the fighters saw the enemy. Command then automatically passed to the fighter leader in the air, who issued orders over the R/T. Once battle was joined the sector controller listened in. If other enemy formations appeared in the air he would inform the fighter leader.

When combat was broken off the controller resumed command and guided the aircraft back to base. If a machine was damaged, the home airfield put out of action or fuel was running low he would direct them to the nearest airfield.

Sectors were only able to deal with four squadrons using ‘Pip-Squeak’. This exhausted the number of automatic transmission periods available. Many times during the Battle of Britain a sector found itself controlling six squadrons in the air. This necessitated quick thinking and much dead reckoning to ensure correct orders for the two squadrons unable to use automatic transmissions for direction finding.

To illustrate the vital and exacting work of sector operations, the following is a dialogue prepared by R.A.F. officers who were controllers during the Battle of Britain.* It faithfully depicts scenes which took place at Biggin Hill during a day in September 1940.

FLOOR SUPERVISOR to Controller: Hostile, sir.

CONTROLLER to Ops B: Ops. B—here they come! Tell the squadrons to be on their toes. I’ve a feeling it’s going to be a repeat of yesterday.

OPS. B to Controller: I’ve already briefed them, sir. Everything’s on the top line and they’re quite ready.—Kenley controller for you, sir.

CONTROLLER: Yes, Kenley? I see, thank you. What do you make of these two raids?—Hostiles 132 and 135? (Slight pause.) Yes, I think so too. It looks fairly obvious from the build-up that they’re intended for us. I expect Group’ll order off something very soon—I’ll let you know.


A photograph taken before the war of the operations room table at No. 11 Fighter Group, Uxbridge. The 11 Group sectors are outlined and the 100 km. squares of British Grid System. In the background is the bottom of the ‘Tote Board’ showing squadrons and their states of readiness

STATION LOOKOUT: Station lookout—testing—testing. Visibility five miles about 3/10th cloud at 20,000 feet. Off.

OPS. A: Biggin Hill—pause—Serial 18—pause—one squadron—intercept hostile 132—Angels 20.† Sir, form A.

CONTROLLER: Right—scramble Tennis squadron, patrol Canterbury Angels 20.

OPS. B: Operations calling—operations calling—Tennis squadron scramble—Tennis squadron scramble—patrol Canterbury Angels 20. One moment, Group—Group controller for you, sir.

CONTROLLER: Smith here, sir.—Getting off now, sir, and the other two squadrons are raring to go. Yes, I think this is it. Right, sir, I’ll expect form A.

OPS. A: Biggin Hill—serial 21—one squadron—intercept raid 135—Angels 20. Sir, form A.

Biggin Hill—serial 24—one squadron—patrol base—Angels 15. Form A, sir.

CONTROLLER: Right—scramble Keta squadron vector 140 Angels 20. Scramble Jaunty squadron patrol base Angels 20.

OPS. B: Keta squadron—scramble—Keta squadron scramble vector 140 make Angels 20.

Jaunty squadron scramble—Jaunty squadron scramble patrol base Angels 20.

Well sir, that’s that—let’s hope that Group’s hunch is right.

CONTROLLER: Guns! All our aircraft are now committed against hostiles 132 and 135. I expect your turn’ll come soon.

GUNS OFFICER: Right sir, I’ll tell gun ops.

STATION LOOKOUT: This is the station lookout—12 Spitfires just took off.

R/T TENNIS LEADER: Hello, Short Jack,* Tennis leader calling, Tennis squadron airborne, making Angels 20—over.

DEPUTY CONTROLLER 1: Hello, Tennis leader, Short Jack answering, loud and clear. Vector 120—60 plus bandits at 15,000 feet heading west—over.

R/T TENNIS LEADER: Hello, Short Jack, O.K. listening out.

R/T KETA LEADER: Hello, Short Jack, Keta leader calling Short Jack, Keta squadron now airborne. Instructions, please—over.

DEPUTY CONTROLLER 11: Hello, Keta leader, Short Jack answering, vector 140—25 plus bandits at 12,000 feet heading west—over.

KETA LEADER: O.K. Short Jack. Listening out.

DEPUTY CONTROLLER 1: Hello, Jaunty leader—correct. Vector 140 Angels 20.

CONTROLLER: Hello, Group. Yes, sir—they’re all off. I understand—we shall do our best. Ops. B—Group Intelligence seem to be right on the ball. They reckon that Hornchurch and ourselves are going to get the lot—I hope they’re wrong. Ops. B—get me the Maidstone Observer Corps centre.

OPS. B: Maidstone, sir.

CONTROLLER: Observer Corps?—This is the Biggin Hill controller—Yes, it is a bit hectic—Group think they’re making for us so keep your tracks going, will you?—You’re doing very well at the moment. Now Ops. B—I want you to ring all dispersals and tell them to get everything into the air that’s serviceable; I don’t want any aircraft to be caught on the ground.


Sir Henry Tizard, an eminent scientist largely responsible for the successful working of the air-defence system


Sir Robert Watson-Watt, who began the radar story and laboured unceasingly on its development

OPS. B: Right away, sir.

CONTROLLER: Group controller?—Biggin here, sir—I’ve ordered all other serviceable aircraft into the air as it looks pretty certain now that these raids are heading for us. By the way, sir—I did tell you that our three squadrons are airborne. Right, thank you, sir.

CONTROLLER: Sergeant Brice. How about 72 squadron—have they had any joy yet?

DEPUTY CONTROLLER 1: Not yet, sir—they are very close—any moment now I think …

TENNIS LEADER: Hello, Short Jack, Tennis leader calling—Tally Ho! Tally Ho! … A gaggle of Heinkels with 109s—Dead ahead. Hell, Tennis squadron, B flight take the bombers, A flight take the fighters with me. A flight, line astern—GO.

CONTROLLER: Guns!—Tennis squadron are now engaging hostile 132 so warn the guns of friendly fighters, will you? How about 32 squadron, Sgt. Norris?—Are they into the others yet?

DEPUTY CONTROLLER 11: Nearly there, sir—Hello, Keta leader, bandits 12 o’clock 15 miles now heading north—Watch out for top fighter cover—over.

KETA LEADER: This is Keta leader—Understood—no joy yet. Keep your eyes skinned, chaps, and don’t straggle. Hello, Short Jack—Keta leader calling—Tally Ho! Tally Ho! A helluva lot of Heinkels and Junkers 88s with fighter escort.

DEPUTY CONTROLLER 11: Hello, Keta leader—Short Jack calling—more friendly fighters are coming to join you. Over.

KETA LEADER: Hello, Short Jack—understood, listening out.

DEPUTY CONTROLLER 1: Hello, Jauuty leader—Short Jack calling—60 plus bandits at 20,000 feet still heading west towards base. Are being engaged by your friends. Any joy yet? Over.

R/T VOICE: Hello, Jaunty leader—Ack Ack fire at 12 o’clock—12 o’clock.

JAUNTY LEADER: Hello, Short Jack—Tally Ho! Tally Ho!—just getting into position. Jaunty squadron, line astern—head on attack—going in … now.

CONTROLLER: Ops. B—Sound the station attack alarm!

OPS. B: This is operations—this is operations. Air raid warning. All station personnel are to take cover immediately.—I repeat—all station personnel are to take cover immediately—enemy attack imminent.

CONTROLLER: Floor supervisor—Get the troops into their battle bowlers right away. Tin hats, everybody.

STATION LOOKOUT: This is the station lookout—enemy aircraft approaching from the south—Five… six… nine… twelve. Blimey, there’s dozens of ’em. Explosions.

TENNIS BLUE 11: MAYDAY—MAYDAY—MAYDAY. Tennis Blue Two calling. Tennis Blue One has baled out—I am orbiting position and transmitting for fix*—my position is just off Deal.

DEPUTY CONTROLLER 1: Hello, Tennis Blue Two—Understood—I have fix on you—stand by.

CONTROLLER: Deal lifeboat?—Biggin here—one of our chaps has baled out off-shore. Yes … in ROBERT 9070† Yes, a Spitfire’s orbiting the position. Good—thank you.

KETA LEADER: Hello Short Jack—Keta leader calling—We have all been split up—aircraft are landing at forward base to re-arm and re-fuel, over.

CONTROLLER: Hello, Keta leader—Short Jack controller answering. Understood. Hello, all Keta aircraft—return to this base immediately after re-fuelling and re-arming. Listening out. Well, George—it’s been quite a morning! Ring the Watch hut and find out how we fared on the airfield.

The efficiency and foresight of group and sector controllers were of prime importance to the conduct of the battle. They had many factors to bear in mind. Squadrons had to be held in reserve to meet fresh attacks. Feints and diversions had to be assessed for what they were. The right moment had to be chosen for a squadron to be recalled to refuel and rearm and fighter endurance had to be taken into account.

In the early stages of the sytem no great care was taken in recruiting controllers, particularly in the sectors. When Dowding arrived in 1936 there were no operations room staff on establishments. Clerks were mainly used. It was, however, quickly realised that a fighter pilot must have complete confidence in the disembodied voice which he heard by radio from sector operations and that the controller must be an experienced man with full knowledge of flying techniques and problems. This evoked resentment in the Signals Branch, who felt that speaking into microphones and pulling radio switches were their prerogatives.

Fortunately good sense prevailed and controllers without flying knowledge were replaced by former pilots of varying ages. When the Battle of Britain opened relations between 11 Group sector controllers and the fighter pilots were excellent. By a curious coincidence six of the seven sectors in 11 Group had on their strength controllers who were former Reserve or Royal Auxiliary Air Force pilots—a great tribute to the abilities of the spare-time airmen.

John Cherry, formerly of No. 604 Squadron, was at North Weald. At Hornchurch and Northolt respectively were Robert Lee and Heath Compton, both from No. 600 Squadron. The former 601 pilots Anthony Norman and P. R. Foley were at Kenley and Biggin Hill, while David Lloyd, who had flown with the Birmingham Air Squadron, was at Tangmere.

* The script for the Battle of Britain sector operations room reproduction on Horseguards Parade, September 1959

* Height 20,000 feet

* Biggin Hill call sign

* Using ‘Pip-Squeak’ and D/F

* Robert = code for 100 km. sided square on the British Grid system. 9070 = a 2 km. sided square within ‘Robert’

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