On 8 February 1955, this first production Valiant was delivered to the RAF. Britain's "V-bomber" force, as it had been nicknamed in October 1952, formally entered operational service on that day. The Victor and Vulcan would soon follow the Valiant into service, for a total of three types of nuclear-armed strategic bombers in RAF service. In September 1957, the final Valiant was delivered. According to Bill Gunston and Peter Gilchrist, all production aircraft had been delivered on time and below budget.