For the first time, here is the true story of the Second World War top secret British invention of the Dome Trainer by Lieutenant Commander Henry Stephens, Royal Navy, from 1939. After naval service in the First World War, including serving on HMS Milbrook at Jutland as a civilian photographer, Henry 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. From early Royal Navy service, a family history as inventors of Stephens Ink and Henry's private journal at the Imperial War Museum, this book brings together new photographs and private correspondence alongside unpublished accounts from those who built and trained with Dome Trainers. The Dome Trainer is placed in context within the offensive and defensive methods developed by Britain, the secret USA Pinball project and recognition by the Cohen Commission of Henry's role as one of the fathers of virtual reality training. In 2015, the BBC broadcast Henry's story in conjunction with the Langham Dome in Norfolk, the only surviving restored and operational unit in Britain.