XD818

XD818 first flew on 4 September 1956 and joined A Flight of No. 49 Squadron at Wittering on 14 November. It was the first of eight Valiants modified for Operation Grapple, the British H-bomb trials. It became the personal aircraft of the squadron commander, Wg Cdr Kenneth Hubbard.

Hubbard flew it to Christmas Island in March 1957. On 15 May 1957 he released the Short Granite device off Malden Island from 45,000 feet. It was Britain's first live thermonuclear drop. XD818 returned for Grapple X in late 1957 and Grapple Y in 1958, when it orbited 50 miles away during another Valiant's drop. In September 1958 it was the observation aircraft for a further test.

The Grapple equipment came out in 1959–60, and it went back to normal bomber training. In 1961 it was converted to tanker standard, and the squadron moved to Marham. By November 1964 it had flown 2,542 hours in 636 flights. Wing spar fatigue grounded every Valiant on 11 December 1964.

XD818 was withdrawn in January 1965 while the rest of the fleet was scrapped. It went on display inside RAF Marham on 25 May 1965. It moved to Hendon in June 1982 for the new Bomber Command Museum, and to Cosford by road in September 2005.

In Hangar 4, the National Cold War Exhibition, in anti-flash white. It is the only complete Valiant anywhere.