720's liquid oxygen. On 16 May 1957, Squadron Leader John Booth DFC was at the controls of XD145 for the first test flight, following up with the maiden flight of the second prototype XD151, on 6 December 1957. During the subsequent flight test programme, these two prototypes flew 56 separate test flights, during which a maximum speed of Mach 1.33 was recorded. Furthermore, since late 1953, Saunders-Roe had worked upon a derivative of the SR.53, which was separately designated as the SR.177; the principal change was the presence of an onboard radar, lacking on the SR.53 and the Avro 720 as it not being a requirement of the specification, but left the pilot dependent on his own vision other than radio-based directions supplied from ground-based radar control. Both the SR.53 and its SR.177 cousin were relatively close to attain production status when wider political factors bore down upon the programme. During 1957, a massive re-thinking of air defence philosophy in Britain occurred, which was embodied in the 1957 Defence White Paper. This paper called for manned combat aircraft to be replaced by missiles, and thus the prospects of an order from the RAF evaporated overnight. While both the Royal Navy and Germany remained potential customers for the SR.177, the confidence of both parties was shaken by the move. Further factors, such as the Lockheed bribery scandals to compel overseas nations to order the Lockheed F-104 Starfighter, also served to undermine the sale prospects of the SR.177, costing potential customers such as Germany and Japan. Throughout the late 1940s and 1950s, the French Air Staff also had considerable interest in rocket-powered aircraft. According to author Michel van Pelt, French Air Force officials were against a pure rocket-powered flight but favoured a mixed-propulsion approach, using a combination of rocket and turbojet engines. While the Société d'Etudes pour la Propulsion par Réaction (SEPR) set about developing France's own domestic rocket engines, the French aircraft manufacturer SNCASE was aware of the French Air Force's keenness for a capable point defence interceptor aircraft, and thus begun work on the SNCASE SE.212 Durandal. In comparison to other French mixed-power experimental aircraft, such as the competing SNCASO Trident prototype interceptor, it was a heavier aircraft, intended to fly primarily on its jet engine rather than its rocket motor. A pair of prototype aircraft were constructed; on 20 April 1956, the first performed its maiden flight, initially flying