This British aircraft was in so many ways the 'almost' aircraft. It almost carried out offensive missions in the war, it almost won one of the largest prizes going, it almost was the first to have a gunner in a rear position. Actually, that's ironic, because when the prototype crashed in Golders Green (north London),only the rear gunner survived. However, it does have one, possibly unique, accolade. Only one of these aircraft ever carried out a raid. A single aircraft, a single raid, but, amazing, this one raid stopped a war.
What's the aircraft?