Tresco Sea Plane Base
During World War I Scilly remained of strategic significance, but for an entirely new form of warfare. Submarines were a threat to allied shipping and aircraft were used to hunt submarines as the wake of a periscope could be seen from the air from several miles away.
In January 1917 a flying boat and seaplane base was created at Porthmellon on St Mary’s, despite warnings that the bay was too exposed. These proved to be well founded and before it became operational the base was transferred to New Grimsby on Tresco. The first patrol was flown on 28 February 1917 and on 18 May 1917 a flying boat from Scilly flew the first escort over a convoy, coming from the Mediterranean. In the last two years of the war aircraft from Scilly made thirteen U-boat sightings and attacked on nine occasions. In one case a U-boat was thought to have been sunk, but it later emerged that the may have survived the attack.
The base at New Grimsby covered the southern part of the bay and consisted of a slipway, hangars, offices, ratings’ and officers’ quarters, a canteen and a sick bay. Little survives today, but The Bothy, a former potato store used for bomb storage, is extant despite being damaged in an explosion. The Power House, another former agricultural building converted for the use of the air base, also survives. The iron rails on the slipway reflect where the flying boats and seaplanes were launched and recovered on trolleys, and a number of concrete standings for other buildings can still be seen at the south end of New Grimbsy.
For more information on Scilly’s rich military history read Defending Scilly by Mark Bowden and Allan Brodie (English Heritage 2011 £9.99)
http://www.english-heritage.org.uk/publications/defending-scilly/