Air Force fleet of English Electric Canberra bombers, largely in response to the Indonesian Air Force's purchase of missile-armed Tupolev Tu-16 bombers. Dassault proposed a version of the Mirage IVA with Rolls-Royce Avon engines. Australian Air Marshall Frederick Scherger seriously considered purchase of the IVA in 1961 because it was considered to be proven hardware already in service (in contrast to the BAC TSR-2 which was still in development), before settling on the General Dynamics F-111C. The IVA was one of five aircraft types that were short listed for the role, but the F-111C was eventually selected. In April 1965, the British Government cancelled the TSR-2 reconnaissance-strike aircraft. However the operational requirement still existed, so in response, Hawker Siddeley offered the Buccaneer S.2, the Americans the General Dynamics F-111K, while, in July 1965, Dassault and British Aircraft Corporation (BAC) jointly proposed a modified Mirage IV. The Dassault/BAC aircraft, known as the Mirage IV* or Mirage IVS (S for Spey) would be re-engined with more powerful Rolls-Royce Spey turbofan engines with a total of , larger (fuselage depth increased by , had an approximately forward fuselage extension, and was to weigh ), and use avionics planned for the TSR-2, although BAC preferred the French Antilope radar. Although designed by Dassault, the production was to be carried out jointly between Dassault and its subcontractors (wing, mid-fuselage, and tail) and BAC (front and rear fuselage). The final assembly location was not determined before this proposal was rejected. The Mirage IV* was to carry a bombload of up to . The Mirage IV* was claimed to meet nearly every RAF requirement except for field length, and some claim it exceeded the F-111 slightly in speed and had at least equal range. The estimated cost was 2.321 million pounds per aircraft (for 50) or 2.067 million (for 110), less than the price of the F-111K. However Air Ministry and RAF studies of the proposal identified further modifications to meet the RAF low-level performance requirements. These included airframe strengthening and revised cockpit glazing to improve visibility for both the pilot and crew member. There was also a significant shortfall in range, despite the lengthened fusealage. BAC claimed that the British government evaluation into the Mirage IV* was "relatively superficial". RAF pilots who test-flew the Mirage IV were "favourably impressed" with its low-altitude handling. However, some British government officials, including Parliament members Julian Risdale and Roy Jenkins,