1943 - 1946: XT Class
During 1943 and 1944, Vickers built six XT-craft submarines for training purposes. Having an endurance of only 500 miles at 4 knots, the XT-boats were a simplified X5 class submarine without the side cargo-release gear, night periscope or automatic helmsman. In addition, their day periscope, projector compass and air-induction trunk were fixed in the 'up' position.
Twelve more vessels, ordered in 1943 from Broadbents of Huddersfield, were cancelled before completion. The six Barrow-boats were scrapped at the end of the war.