Aiming an anti aircraft gun is a complicated mathematical problem. One cannot simply aim at the plane since by the time the bullet reaches that point, the plane would be long gone, particularly in the case of the dive-bombers the Germans used in World War II. In the Westwood underground factory, Royal Enfield manufactured analog computers to aim anti aircraft guns. The type they built are called Kerrison predictors, models No. 3 and No. 7. The Kerrison predictors were developed by Sperry in the US and used by both US and UK forces. The picture above is from a booklet that Royal Enfield produced after the war documenting its war efforts (see David Blasco's report on it). Unfortunately the booklet is quite thin and information about these projects is incredibly scant. The box behind the predictor was the electric generator. Enfield used to supply those as well, with two stroke gas engines, which the soldiers usually forgot to feed with oil mixed with the gas, leading to engine seizures. The Wessex Stationary Engine Club had one for sale in 2007. The person selling it claims only a handful of Kerrison predictors are left nowadays. Later in the war predictors were connected to radar and could read the coordinates of the plane directly, allowing to shoot to planes that cannot be seen. Presumably the tower behind the Enfield predictor in the top photo is for radar. The booklet comments "The Company emerges from the war with an increase in productive capacity which, coupled with six years' experience in the manufacture of Fire Control Instruments of the highest precision, will ensure that ROYAL ENFIELD Bicycles, Motor Cycles and Lawn Mowers will soon be available in large quantities and of the highest standards of excellence."