This episode examines how war can bring with it innovation as well as horror. It tells the story of some of the scientists and engineers who helped Britain win the Second World War, and how we have enjoyed the benefits of their discoveries to this day. Richard Dawkins reveals his admiration for Alan Turing, the man who pioneered modern computing science as a by-product of his work deciphering the German Enigma Code at Bletchley Park. James Dyson celebrates the work of engineer Frank Whittle, who came from nowhere to invent the jet engine, and experiences the incredible power of Whittle's invention for himself in an RAF jet. Jim Al-Khalili reveals how, without the discovery of radar by Robert Watson-Watt, the Battle of Britain would certainly have been lost. Kathy Sykes explains how Paul Dirac tried to combine the seemingly incompatible worlds of relativity and quantum mechanics, and helped to pave the way for modern electronics. And Paul Nurse tells the true story of Alexander Fleming, whose discovery of penicillin went on to save the lives of hundreds of thousands of fighting men, as well as millions more people since.