a development contract had been placed for the P.1154, equipped with the BS100 engine, as an RAF strike aircraft. At the same time, it was announced that the Naval requirement would instead be met by Spey-engined Phantoms. Wood stated that this decision was "the beginning of the end for the 1154 as the original operation requirement was for joint-service use". In the aftermath of the government announcement, HSA persisted with work on the P.1154. By September 1964, the first full-scale mock-up meeting had been conducted. On 30 October 1964, a milestone in the development programme was attained when the first run of a BS100 engine was performed; around the same time, HSA received favourable reports that the P.1154 was competitive with the performance of other aircraft, including the F-4 Phantom II. The P.1154 ultimately became a victim of the incoming Labour government, led by Harold Wilson. In November 1964, Wilson's government informed the Air Staff to prepare to cancel two of three specific ongoing development projects, these being the P.1154, the BAC TSR-2 strike aircraft, and the Hawker Siddeley HS.681 V/STOL transport aircraft; in order to save the TSR-2 programme, the RAF was satisfied to abandon the P.1154. On 2 February 1965, it was announced that the P.1154 had been terminated on the grounds of cost. At the time of cancellation, at least three prototypes had reached various stages of construction. Following the cancellation, the RAF adopted the F-4 Phantom II ( as ordered by the RN) instead; however, the government also issued a contract for continued work on the original subsonic P.1127 (RAF), which led to the Harrier; this name had originally been reserved for the P.1154 should it enter service. In retrospect, aviation author Tony Buttler considered the cancellation of the aircraft to be justified, noting the time-consuming and expensive failures of attempts by other nations (such as Soviet/Russia's Yak-41 and West Germany's EWR VJ 101) at a supersonic VTOL aircraft. These aircraft all used a multiple engines configuration like the Mirage IIIV, and not the single vectored thrust turbofan of the likes of the BS.100 and Pegasus which went on to great success in the Harrier. Wood described the overall situation as: "From start to finish the P.1154 programme was a story of delay, ministerial interference and indecision... the P.1150 would now be the ideal aircraft for the new generation through-deck cruisers" Specifications (P.1154 – RAF version)