How the British Home Defence System Worked

The image below depicts the co-ordination of the various elements of the British Home Defence Forces. First, the Observer Corps, at the coast, reported to Central Control Headquarters, giving information on the approach of enemy aircraft. Headquarters then telephoned the appropriate searchlight and anti-aircraft batteries, and fighter plane stations. Sound locators automatically trained searchlights on the raiders, and predictors and range finders directed gunfire. Fire ceased as interceptor fighters swooped in to attack.

Note that the sequence of operations described on this page only provided for up to about 10 minutes' warning before the target was reached by the attacking aircraft, since the aircraft were not spotted until they were almost at the coast. Later in the war, with the advent of radar, attacking aircraft could be spotted up to 200 miles away, which allowed for a much longer warning period before the planes arrived at the target.