The A.27 London was designed in response to the Air Ministry Specification R.24/31[REF][REF] issued for a "General Purpose Open Sea Patrol Flying Boat" and was based on the Saro A.7 Severn.
The first prototype first flew in March 1934 and then went on to serve until 1936 with 209 and 210 Squadrons RAF at RAF Felixstowe and Gibraltar respectively.