After an initial rejection by the Air Ministry, Supermarine persisted with development as a private venture under the designation Southampton V. During 1933, a contract was placed for a single prototype; it was around this time that the type was named after Stranraer.

These Canadian Stranraers served in anti-submarine and coastal defence capacities on both Canada's Atlantic and Pacific coasts, and were in regular service until 1946.

Following their withdrawal from military service, many ex-RCAF Stranraers were sold off to fledgling regional airlines, with whom they served in various commercial passenger and freighter operations into the 1950s.

[4] The project was pursued as a response to the Air Ministry's issuing of Specification R.24/31 in 1931,[5] which called for a general purpose coastal reconnaissance flying boat for the RAF.

Supermarine's initial response to the specification was a larger model of the Scapa; the company competed against a bid from Saunders-Roe.

On 24 October 1934 it was delivered to the Marine Aircraft Experimental Establishment (MAEE) at RAF Felixstowe for official trials.

[10] The first production standard aircraft made its first flight in December 1936, and entered service operation with the RAF on 16 April 1937.

The Rolls-Royce Kestrel was initially considered as a powerplant, but eventually the moderately supercharged Bristol Pegasus IIIM radial engine was selected, .

[14] Much of the airframe was alclad, while detailed fittings were made of stainless steel; metal components were anodised as an anti-corrosion measure.

[7] The production model of the Stranraer was different in a few aspects from the first prototype, chiefly of which being the installation of the more powerful 920 horsepower (690 kW) Pegasus X engine.

[6] Immediately following the outbreak of the war in September 1939, Stranraers patrolled the North Sea, intercepting enemy shipping between Scotland and Norway.

[9] Having acquired a less than favourable reception by flight and ground crews alike, the Stranraer gained a large number of derisive nicknames during its service life.

In Canadian service, they were usually employed in coastal patrol against submarine threats in a similar role to the British Stranraers.

[23] However, the crew of a 5 Squadron Stranraer, flown by Flight Lieutenant Leonard Birchall, were responsible for the capture of an Italian merchant ship, the Capo Nola, in the Gulf of Saint Lawrence, hours after Canada issued its declaration of war on Italy on 10 June 1940.

In November 1944, 20 aircraft that had been withdrawn from active service in February earlier that year were purchased for civilian use, before being registered in Canada or the US.

[26] After the end of World War II, 13 examples were sold through Crown Assets (Canadian government) and passed into civilian use; several served with Queen Charlotte Airlines (QCA) in British Columbia, operating until 1958.

[27] A re-engine project by the airline substituted 1,200 horsepower (890 kW) Wright GR-1820-G202GA engines in place of the original Pegasus units.

Queen Charlotte Airlines flew the aircraft on passenger flights until 1952, flying from Vancouver along the Pacific coast of British Columbia.

This aircraft also operated with Queen Charlotte Airlines until it crashed on Christmas Eve 1949 at Belize Inlet, British Columbia.