A major problem with the use of destroyers for escort work in the North Atlantic was their lack of endurance .
Vanoc was converted to a long - range escort at Thornycroft 's Southampton shipyard between April and November 1943 .
A major problem with the use of destroyers for escort work in the North Atlantic was their lack of endurance , and Vanoc was converted to a long - range escort at Thornycroft 's Southampton shipyard between April and November 1943 .