Since the paragraph on the Swift in "Aircraft Intelligence" (page 331) went to press, an official announcement by Vickers-Armstrongs has stated that the aircraft has exceeded the speed of sound "on a number of occasions," and that Mike Lithgow and Dave Morgan were the pilots on these flights.
For residents near the Supermarine airfields this comes as further confirmation of the news implied by the bangs they have been hearing recently. Listeners to the Western Regional B.B.C. services also received advance notice of the official statement; it came during a broadcast commentary of a recent football match at Swindon, when the alleged boredom of a quiet match was relieved by supersonic barracking from a Swift overhead.
Source: Flight International