The aircraft was designed to specification R.24/31 filling the need
for a twin-engined coastal reconnaissance flying boat. Features were
robustness, simplicity of construction and low maintenance costs. The
prototype, registered K3560 and powered by two 750 hp Bristol Pegasus
III radials, flew for the first time in 1934 and a production order
was placed in March 1935, receiving the name London.
The first London Mk.I production models were also powered by the
Pegasus III, the first flew early 1936, starting service with RAF
coastal squadrons in April 1936. From the eleventh production
aircraft the type was build to specification R.3/35 as Mk.IIs with
Pegasus X engines, having as the most distinctive external difference
the nine-angled engine cowlings being replaced by circular ones.
The original prototype and the ten Mk.Is were converted to Mk.IIs. A
total of 49 Londons were built, including the prototype. The last
London was withdrawn from service in June 1941.
The aircraft was of all-metal construction with fabric-covered wing
and tail surfaces. It had a crew of 6 and was armed with three .303
in (7.7 mm) Lewis machine-guns in the bow, dorsal and tail positions.
A maximum 2,000 lb (907 kg) load of bombs, depth charges or mines
could be carried.