Designed to the same specification, R. 24/31, as the Saro London, the Supermarine Stranraer twin-engine biplane flying-boat survived in service slightly longer than the other, and was generally preferred by those crews who were able to compare the two types. The prototype, originally known as the Singapore V, was powered by Bristol Pegasus HIM radials driving two-blade wooden propellers and first flew in mid-1935, but was immediately renamed Stranraer. It also underwent comparative trials with the London on No. 210 Squadron in October and November 1935, during which it was found to be somewhat underpowered. Production deliveries of aircraft powered by a pair of Pegasus X radials driving a three-blade Fairey Reed metal propeller started December 1936, and the type was declared operational in April the following year with No. 228 Squadron at Pembroke Dock, remaining with this squadron until April 1939, In December 1938 Stranraers joined No. 209 Squadron at Felixstowe, and later moving to Invergordon and Oban for patrols over the North Sea until supplanted by the ill-fated Lerwick the following year. No, 240 Squadron was the only other RAF Coastal Command squadron to fly the Stranraer, converting to the aircraft in June 1940 at Pembroke Dock for short-range patrol work over the Western Approaches; the Stranraers were eventually replaced by Catalina 'boats in March 1941, Although RAF Stranraers did not serve at overseas stations, a total of 40 aircraft was licence-built by Canadian-Vickers between 1939 and 1941, and served in the coastal reconnaissance/anti-submarine role with the RCAF until finally replaced by the Consolidated Canso (Catalina) during 1943.