The Valentine DD was the first production version of the floating tanks that saw action on D-Day when applied to the Sherman tank.
The DD device was invented by Nicholas Straussler. A collapsible canvas screen was attached to the waterproofed hull. A screw propeller, powered by the main tank engine, provided power in the water. The screen was raised by using compressed air to fill rubber tubes, and could easily be lowered by letting the air out of the tubes.
The DD equipment was tested on a Tetrarch light tank in June 1941. These were successful, and the type was then ordered into production, using the Valentine tank. The first contract, for 450 conversions, was placed in the summer of 1942.
625 Valentines were converted into DD tanks by Metropolitan-Cammell, one of the firms that constructed the tank. Some were based on the 2-pounder versions, others on the 6-pounder Mk IX and the last produced on the 75mm Mk XI.
The Valentine DD was mainly used for training. It had been replaced by the Sherman DD tank in Britain before D-Day, but the Valentine version did see some combat in Italy in 1945. A total of 105 Valentine DD tanks went to Italy, where 75 were allocated to operation units and 30 to training units.