It was designed to meet an Air Ministry requirement (defined in Specification R.14/40) for a very-long range reconnaissance flying boat.
Two prototypes flew, but the end of World War II prevented the Shetland from entering production.
The aircraft flew without gun turrets (its role having been revised to that of unarmed transport before its maiden flight.
Testing indicated satisfactory water handling but the stabilising floats were mounted too low and did not offer sufficient clearance for takeoffs with maximum load.
With the end of the war, the second prototype (serial number DX171) was completed as a civil transport and designated Shetland II.