Boxer was the next in development of the tank landing ship following the conversion of the Maracaibo tankers into landing ships capable of carrying vehicles. The requirement was for a ship that could carry 13 Churchill tanks, 27 other vehicles and 193 men. As it was expected to have a high speed even when laden for the assault (about 18 knots) it could not have a shallow draught. This in turn meant that an extra long bow ramp had to be added. At 140 ft (43 m) this took up a lot of room inside the ship.
Boxer had only two sister ships, as plans to build more in the United States led instead to a simpler though slower design capable of similar capacity but with a much shallower draught.