What stopped Hitler in 1940 - why did he not attempt to invade Britain? In this fresh look, Derek Robinson argues that the Battle of Britain alone could not have been why Operation Sealion, the planned German invasion, was scrapped. The real reason was a force that both Churchill and Hitler failed to acknowledge: the Royal Navy. Whilst never downplaying the skill and courage of the pilots who fought in the Battle of Britain, Robinson challenges a verdit that has been in place for 50 years, and make us question our acceptance of the old story.