Free The Battle of Britain by Bickers Richard Townshend

raid.
    â€˜Information required by the three Groups will be obtained by at least 15 RDF stations, the observers (NB: the people who read the display on the cathode ray tube) at which, in time of high raid density, will tell plots at a high rate. This information is to be filtered and passed accurately and speedily to Groups and Sectors simultaneously. This means that on the average, when stations are all bringing in raids, the Group teller will have to tell information received from 5 RDF stations and will therefore have to tell information at five times the rate of the RDF observers.
    â€˜A Sector requires information accurately and speedily at the rate of one plot per minute per raid. If each Sector can handle even four simultaneous raids, plots must be received at the rate of four per minute.’
    No. 11 Gp had six sectors; Nos. 12 and 13 had three each. Hence the Filter Room had to pass plots at the rate of 12 per minute to Nos. 12 and 13 Gps, and 24 per minute to No. 11 if all Sectors were to be able to work to capacity. These were only the plots required by Sectors for interception, but there would also be information on distant approaching raids to tell.
    In July 1940 Nos. 12 and 13 Gps each had six Sectors and No. 11 had eight. By the following month, with No. 10 Gp operational, three more Sectors were added. No. 10 in fact had four Sectors, but one of these had formerly been in No. 11, which now was reduced to seven. With four groups totalling 27 Sectors, it is clear why careful selection of radar operators, plotters and filterers was essential.
    When the war began, the control and reporting system, the most sophisticated in the world, was fuctioning smoothly. By the time the first sorties in the Battle of Britain were flown, it had reached a degree of efficiency far higher than that of the equivalent German organisation.
    The Women’s Auxiliary Air Force provided an increasingly large proportion of the personnel employed within it, at radar stations and Filter and Operations Rooms. This body, formed on June 28, 1939, was the successor to the Women’s Royal Flying Corps of World War I, which had become the Women’s Royal Air Force in 1918 and been disbanded in 1920. When three typists in the early days at Bawdsey had been trained to read and tell the responses on a cathode ray tube, it became apparent that women adapted better in many ways than men to this type of work.
    The young women selected to be ‘Clerks, Special Duties’, their camouflaged job description, and known less pompously as ‘plotters’, had to have a higher than average educational standard. Predominantly, they belonged to the class that their comrades described as ‘boarding school girls’. To the pilots, who were supposed to visit the Ops Room frequently, in order to understand the difficulties of the Controllers’ job, they were ‘the beauty chorus’ and it was more the sight of a group of attractive girls than duty that drew the young men there.
    The Observer Corps was organised in posts and groups. The system was fully tested during the exercise in August 1939. Secrecy about radar was so strict that, although the Corps was under the Air Ministry and received information from the radar chain, only a few officers were allowed to know the details of how this was obtained.
    Posts were sited at any convenient place that allowed a good field of view: rooftops were good vantage points. They were not comfortableplaces in which to spend several hours at a time. In a small sandbagged enclosure with scant weather protection, equipped with an instrument for estimating height and position of aircraft, binoculars and a telephone, these dedicated men kept watch. Every group HQ had a centre where 12 plotters seated around a map table each received information from two or three posts, thus co-ordinating the efforts of about 30 posts.
    Here again, the problem of duplication had to be resolved. A teller passed