In 1928 a Supermarine Southampton was flown with an experimental weight saving hull. This designated A.14 and had been designed and built by Saunders-Roe. Successful testing of this aircraft encouraged design in 1930 of the Saro A.7 Severn, a military flying boat of sesquiplane configuration that incorporated an almost identical hull and had a powerplant of three 485 hp (362 kW) Bristol Jupiter IX radial engines. Its performance was better the twin engine Southamptons and comparable with the three engined Southampton X but, presumably because the Supermarine aircraft were already in production for the Royal Air Force, no orders were received for the Saro A.7 Severn. With the issue of Air Ministry Specification R.24/31 for a coastal patrol flying boat Saunders-Roe designated the A.27 London which, of similar configuration and only slightly smaller in size than the A.7 Severn from which it was developed. The prototype London flew for the first time in 1934 and the type was ordered into production in the following March.


Deliveries began in 1936 and the first 10 aircraft were designated London Mk Is. Construction Nos 11 to 48 (the final production London) were all London Mk IIs, which differed in having 915 hp (682 kW) Bristol Pegasus X engines driving four-bladed propellers, in place of the London Mk I's 820 hp (611 kW) Pegasus III engines with two-bladed propellers.(Later fitted with three bladed propellers)








First service deliveries, between April and September 1936, were to No. 201 Squadron, replacing Supermarine Southamptons at Calshot with further batches delivered in October 1936 to No. 204 Squadron at Mount Batten, Plymouth, also replacing Southamptons. More were delivered to the same squadron at Mount Batten the following year to replace Blackbum Perths, and in 1938 the London Mk IIs supplanted Supermarine Scapas of No. 202 Squadron in Malta.

No.204 Squadron used five Londons on a long-distance training flight to New South Wales, Australia and back between December 1937 and May 1938. They were fitted with exteral overload tanks to increase thier range to 2,600 miles (4184 km).

Between the two World Wars the flying-boat reigned supreme for coastal patrol work with the RAF, and the Saro London, together with its contemporary, the Supermarine Stranraer, were the last of the biplane flying-boats to see service before replacement by the Short Sunderland. Twenty-nine Londons were still in service at the outbreak of World War II.

Nos. 201, 202, and 240 squadrons were still operating Londons in first-line service at the outbreak of World War II, flying patrols over the Straits of Gibraltar and the North Sea. They were eventually retired early in 1941 when they were replaced by the Consolidated Catalina . At this time a number of the Londons were transferred to the Royal Canadian Air Force.























One of the aircraft on the long-distance training flight to Australia to celebrate the 150th anniversary of the founding of the Colony at Sydney, New South Wales, had engine problems throwing a propeller which impacted the top port wing, the aircraft landed safely and was repaired.



Specifications (London Mk.II)
General characteristics
Crew: 6
Length: 56 ft 6 in (17.22 m)
Wingspan: 80 ft 0 in (24.38 m)
Height: 18 ft 9 in (5.72 m)
Wing area: 1,425 sq ft (132.4 m2)
Empty weight: 11,100 lb (5,035 kg)
Gross weight: 18,400 lb (8,346 kg)
Powerplant: 2 × Bristol Pegasus X 9-cylinder air-cooled radial piston engines, 915 hp (682 kW) each
Propellers: 3-bladed fixed-pitch propellers
Performance
Maximum speed: 155 mph (249 km/h, 135 kn)
Cruise speed: 128 mph (206 km/h, 111 kn)
Range: 1,100 mi (1,800 km, 960 nmi)
Ferry range: 1,740 mi (2,800 km, 1,510 nmi) with auxiliary fuel tank over fuselage
Service ceiling: 19,900 ft (6,100 m)
Rate of climb: 1,180 ft/min (6.0 m/s)
Armament
Guns: 3 × Lewis guns
Bombs: 2,000 lb (900 kg) of bombs, mines or depth charges
(text from here - http://www.century-of-flight.freeola.com/Aviation%20history/photo_albums/timeline/ww2/Saro%20A.27%20London.htm)