The fixed AA defences gradually increased throughout 1915 and by November the total number of guns and searchlights employed was:
11 3” Q.F. guns
4 6 pdr Q.F. guns
13 twin 24” lights
14 single 24” lights
The guns and lights were positioned in a central belt and a belt of five miles from the centre. Accommodation consisting of living and sleeping quarters was provided at each gun site. Central control was at the Admiralty. Direct telephone lines ran to District Controls. Each District Control was in charge of a Lieutenant who was responsible for the control of the guns and searchlights in his District. However authority was delegated to officers at the Gun Stations to open fire and switch on searchlights if a Zeppelin was sighted. Searchlights were powered either by motor generator or consisted of self contained plant with oil or gas engines.
Above: Sketch map of London's AA Defences, Nov 1915
As well as the established guns and lights, other positions were in the process of being constructed, including a nine mile circle from the centre. As well as single gun stations, battery positions of four 6 pdr guns and 3” guns were being prepared. It was recognised that to deter Zeppelins from attacking London, there had to be a reasonable chance of hitting one, to make them think twice; batteries of four or more guns was considered the best way to meet this purpose.
By March 1916 it was hoped to have the following guns and lights in place for the defence of London:
10 4.7” guns
8 4” guns
20 3” guns (including two batteries of four guns)
36 6 pdr guns (including eight batteries of four guns)
7 36” searchlights
27 single 24” searchlights
17 twin 24” searchlights
Even this was regarded as inadequate and a further 96 guns on fixed mountings and 15 guns on mobile mountings were ordered at the end of 1915.