In May 1954, "WG760" and its support equipment were moved to RAF Boscombe Down for pre-flight ground taxi trials; on the morning of 4 August 1954, "WG760", piloted by Roland Beamont, flew for the first time from Boscombe Down. One week later, "WG760" officially achieved supersonic flight for the first time, having exceeded the speed of sound during its third flight. During its first flight, "WG760" had unknowingly exceeded , but due to position error the Mach meter only showed a maximum of . The occurrence was noticed during flight data analysis a few days later. While "WG760" had proven the P.1 design to be viable, it was limited to due to directional stability limits. In May 1956, the P.1 received the "Lightning" name, which was said to have been partially selected to reflect the aircraft's supersonic capabilities.