Our next open day is in:


Air Raid Warning Systems in Croydon: From non-existence to technical wizardry


Records in the Museum of Croydon record the gradual implementation of an air raid defence system and even – though not until summer 1917 – public air raid warnings. Our project volunteer Norman has recorded the growth of these defences, which consisted of Observation Posts, Special Constables, the airfield itself and a growth in the use of light and sound technology to track and monitor aircraft.

Observation Posts in Croydon

View from the Town Hall Croydon in 1938.
  • Town Hall Tower
  • Water Tower
  • Gillett & Johnston’s Tower
  • Nottingham Road

Observer duties included observing and reporting on hostile flying machines, exposed lights, fires etc. Reported by telephone to Observation Room, Croydon; Metropolitan Observation Service, Horseguards (forerunner of Observer (later Royal) Corps); Regular Police and Fire Service.

Special Constabulary station and posts
Police Station, Fell Road; Trojan Works, Vicarage Road, Waddon; Christ Church Schools, Clyde Road; Addiscombe Railway Station; Wesleyan Hall, Bartlett Street, South Croydon.

The Special Constabulary were appointed at start of war, they carried out normal policing duties (traffic accidents, carts without lights, drunken soldiers, small boys stealing bicycle) but their principal activities were war-related.

They also manned Observation Posts, reporting hostile aircraft (Zeppelins and Gothas) and breaches of blackout (mostly careless or false alarm by nervous citizens) but always alert to “spies” signalling to Zeppelins.  They guarded key installations though there are no records of their being armed.  They also assisted in rescuing or recovering bombing victims. Specials also controlled mobile first aid parties including St John and Red Cross, Voluntary Aid Detachment (nurses) and a Motor Branch.
When raids were believed to be imminent, Specials were summoned by telephone, personal visit or boards in cinemas and clubs. During the Great War, Croydon Specials paraded for air raid duties on 63 occasions and were on stand-by a further 15 times. An average parade for air raids would comprise 250-300 men (only men).

Air Raid Warnings

by Walter Bayes. Imperial War Museum. Art.IWM ART 935

From June 1917 the police gave raid warnings by firing maroons. Boy Scouts played Morse G-C on bugles for all clear. A red light displayed from Town Hall clock tower during Alert and white for All Clear. In addition the Town Hall basement was sand-bagged as air raid shelter.

A mobile A.A. Based at White Hill Caterham comprising 2 lorries each with 2 machine-guns; one lorry with 24” acetylene searchlight; service wagon for cooking, sleeping and stores

Air defence: Tram with searchlight installed upper deck
Searchlights seen flashing as signal to recall night fighters

Fire Alarms were installed on on street corners before advent of home and street telephone call boxes.

Each Observation Post was eventually equipped with a telescope with illuminated sights and the base was marked with compass degrees. A sighting would be reported by telephone (or runner) to the Chief Inspector of the Regular Police. His station was equipped with a large-scale map and by receiving bearings from two or more Observation Posts, the location of any incident could be plotted with cords on the map by triangulation [see exhibit in Control Tower]. An example of this was when an incendiary bomb caused a fire on railway truck four miles away, the location of which was plotted by central control within four minutes. Also Zeppelin crashes to north of London observed and accurately plotted. Sighting reports were forwarded to London Air Defence Area headquarters in Horseguards.

Nottingham Road Observation Post was also fitted with “sound detectors” (giant horns) to track enemy aircraft.

Water Tower Observation Post had automatic equipment to record bearing and azimuth of targets and weather reports.

Norman Brice

More to explorer