Vickers-Armstrong Ltd., Not Published, Barrow-n-Furness, 1947. 31 pp + 14 drawings, diagrams, graphs, etc. (all fldg.). Original p.c., 34 x 22cm. V.G. The Royal Navy's 'T' class (or Triton class) diesel-electric submarine was designed in the 1930s to replace the 'O', 'P' and 'R' classes. Before and during the war, 53 boats of this class were built for the Navy and played a major role in British submarine operations. A further 4 were in service in the Royal Netherlands Navy known as the Zwaardfish class. In the decade following the war, when this builder's shipyard manual was produced, the oldest surviving boats were scrapped and the remainder converted to anti-submarine vessels to counter the growing Soviet threat. The last of the 'T' class was disposed of in 1969 although a permanently moored boat was used for training purposes until 1974. The last of them all was serving in the Israel Sea Corps until 1977. With a range of 8,000 nautical miles and with a complement of 48 men, these submarines were armed with 6 bow torpedo tubes, 4 external tubes, carried 16 torpedoes and a QF 4-inch deck gun. Perhaps the most well-known of the class was the THETIS, lost in Liverpool Bay on her trials in 1939, raised, re-named, and lost to enemy action in the Mediterranean in 1942. This manual marked "Return to Safe" was in use in 1947 at Barrow at the time of the transfers to the Dutch Navy. It covers in detail the engines of these famous submarines : their fuel injection system, spray valves, fuel pumps, inlet and exhaust valves, water circulation, engine output, avoidance of over-loading and over-speeding, turning gear, salt water leaks, securities, compression pressure, etc. The manual is illustrated with 14 folding drawings and diagrams, etc.