Considered an important testbed for high-speed flight, "VW120" was readied for an attempt at the World Speed Record then held by a Gloster Meteor at 616 mph (991 km/h). The second prototype, "TG306", was a "backup" for the attempt before it fatally crashed. On 12 April 1948, "VW120" established a new World Air Speed Record of 604.98 mph (974.02 km/h) on a 62-mile (100 km) circuit. Then, on 6 September 1948, John Derry is thought to have probably exceeded the speed of sound in a shallow dive from 40,000 ft (12,195 m) to 30,000 ft (9,145 m). The test pilot Captain Eric "Winkle" Brown, who escaped a crash in 1949, described the DH 108 as "a killer".