The Boulton Paul Defiant was a British fighter aircraft and bomber interceptor used early in the Second World War. The Defiant was designed and built by Boulton Paul Aircraft as a "turret fighter" and served with the Royal Air Force. Contemporary with the Royal Navy's Blackburn Roc, the concept of a turret fighter was somewhat similar to the First World War-era Bristol Fighter. In practice, the Defiant was found to be vulnerable to the Luftwaffe's more agile, single-seat Messerschmitt Bf 109 fighters; crucially, the Defiant did not have any forward-firing guns. It was later used successfully in the night fighter role, before it was phased out of combat service in favour of the Bristol Beaufighter and de Havilland Mosquito. The Defiant finally found use in gunnery training, target towing, ECM and air-sea rescue. Among RAF pilots, it had the nickname "Daffy", probably a dimunitive of the word "Defiant".