Duncan McC's correct(of course)-she would go very fast and 600kts was attainable but didn't turn too well.Collected the penultimate aircraft from H on S for 208 Sqn and the Waste of Space clean fit was" very impressive" said Ramjet my driver for the day.I didn't clock the actual max IAS on the long run back to Honington-busy completing the post manufacturers flight test and max speed required (from memory) was 540kts.By the time the RAF gingerbeers had "re-roled" the beast it never performed as well. Flew in the Warton tanker many years later and she went very fast,clean.
Those were the days!