ww2 british T class submarine cutaway plan

T class submarine in plan, originally uploaded by daviddb.

The Royal Navy's T class (or Triton class) of submarines was designed in the 1930s
constrained by the 1930 London Naval Treaty restricting the total British submarine fleet to 52,700 tons, a maximum of 2,000 tons for any boat, and maximum armament of one 5.1 inch (130 mm) gun. The "Repeat P"s, as the design was originally called, were intended to be large and powerful enough to operate against Japan in the absence of other British naval units. This demanded a large boat with impressive firepower, and the eventual design had 10 forward-facing torpedo tubes and a maximum diving depth of 300 ft (91 m).
The lead boat, Triton, was ordered March 5, 1936 and ran her first-of-class trials in December 1938. Fifty-three T-class submarines were built before and during the war in three distinct groups.