Civil Defence, wide though its activities became, was but one of a number of services defending Britain against air attack. The part of the Royal Air Force in this campaign was, of course, pre-eminent; and that of the Army's Anti-Aircraft Command was of almost equal importance. The Royal Observer Corps, under the control of Fighter Command, was the primary source of intelligence for the whole defence system about the movement of hostile aircraft over Britain.
In the First World War the collection of information about hostile aircraft and its distribution had been performed mainly through an elaborate system of observer posts, and this system had been kept in being in a small area as an 'Observer Corps', composed of volunteers enrolled as special constables.
The ARP committee in its first report in 1925 proposed the setting up of a further system of observation posts that could be most efficiently worked through the police. Volunteers enrolled as special constables manned the new network of such posts in Kent and Sussex.
By the autumn of 1932 the most active development of the warning system related to the collection of information. Responsibility for this function had been transferred in 1929 from the War Office to the Air Ministry. In that part of England considered within range of hostile bombers the observation system, manned by volunteers of the Observer Corps, was in a sufficiently advanced state to be put into operation at any time.
The Corps had since proved its efficiency in annual R.A.F. exercises; and it would form an important source of intelligence, for both active and passive defence, of the movements during another war of friendly as well as hostile aircraft.
By the beginning of 1935 the Observer Corps had only been developed for parts of the southern and eastern English coasts and the counties bordering London; though its expansion in line with the general expansion of the R.A.F. had been recommended. The Home Office, as the authority responsible for the distribution of air raid warnings, was eager for this expansion and consulted the Air Ministry. After much discussion, these departments submitted a joint proposal to the Committee for Imperial Defence for extension of the Observer Corps to cover virtually all England and Wales and Eastern Scotland. The Committee gave its approval in July 1937 - certain new Groups of the Corps in the West Country, Wales and Scotland were created solely to meet Home Office needs for rapid and adequate civilian air raid warning.
On the 26 September 1938, following the Munich Crisis, the Observer Corps and the anti-aircraft units of the Territorial Army were called out, and the warning system for eastern parts of the country was brought to a state of readiness. Once the crisis had subsided further improvements were made in the telephone and other technical facilities.
Ten days before war finally broke out all was put into readiness. Responsibility for initiating all air raid messages would rest with Fighter Command, who would be told of the approach and course of enemy aircraft first by radar as they approached the chain of radar stations monitoring aircraft out to sea and then the Observer Corps once the aircraft were over land.
In recognition of its service in the preceding years, the Observer Corps had been granted the title Royal Observer Corps in April 1941
By July 4, 1941 the decision had been made to decentralise responsibility for initiating warnings. This decision had been brought about by the enemy deliberately sending one or two aircraft to zigzag over the country to cause industrial dislocation. 'Alarm Officers' were appointed to each Region and 'Alarm Controllers' to many Observer Corps Centres in the country. The function of these Controllers became that of passing on information regarding impending attacks to a central control point. By the end of 1942 this system embraced much of the vital production of the country and had proved a genuine success.
By 1943, air attack in Britain had become progressively smaller in scale, though the threat of some 500 enemy aircraft capable of making a sudden effective onslaught on say London remained. The tip and run form of attack that Britain was now experiencing set difficult problems in the matter of warning, especially as the enemy, flying low over the Channel at a speed of 300 m.p.h., or more was temporarily able to defeat the radar system. An adjustment, which brought considerable improvement, extended in certain places the decentralisation of the system already under way. Observer Centres in certain southern and eastern coastal areas were linked by direct line with the telephone exchanges from which warning messages were distributed, and the alarm controllers stationed at these were permitted to issue the 'red' air-raid warning.
Decentralisation of the system on a national basis through transfer of responsibility from Fighter Group headquarters to Observer Corps Centres was also being planned. The ever-increasing speed of aircraft made it essential to hasten this process, so as to eliminate delays in transmitting intelligence about the movement of enemy aircraft. This changeover was completed by April 1944 in the 36 Royal Observer Corps Centres. The former alarm controllers then became Home Security warning officers.
Copyright © 2002 Peter N. Risbey.