The secret dome : ant-aircraft gunnery training in the Second World War /Ewan Ward-Thomas.

"After naval service in the First World War, including serving on HMS Milbrook at Jutland as a civilian photographer, Henry [Stephens] recognised the nascent threat to a ship from Luftwaffe aircraft flown in the Spanish Civil War, and so developed an indoor cinema to project attacking aircraft and to train gunners. The Royal Navy ordered Henry to re-enlist and secretly develop his Dome Trainer, recognising the imperative to defend shipping from airborne attack. Consequently, the Dome Trainer technology became the standard "synthetic" weatherproof anti-aircraft training solution. 300 units were deployed around the world, including Sydney, Bombay, Newfoundland and Durban, training Defensively Armed Merchant Ships (DAMS) within crucial Atlantic merchant navy convoys sailing from Britain and the east coast of the USA and Canada. The Maritime Royal Artillery (MRA) was formed in January 1943 for 24 ports with 14,000 men" --