The Canadian Sexton Self Propelled Gun (SPG) was constructed to utilize a 25-pound round, the same ammunition being used as a standard caliber in the British Army in order to replace American Priest and failed Bishop. So, US Army and the Canadian Government's Department of Munitions and Supply were designing an SPG version using the 25-Pounder gun on an American M3 Lee medium tank body. The 25-pounder prototype underwent firing trials and was found to be suitable to the British needs, who in turn ordered 300 units in May of 1943 and designated it as the "Sexton". The first order of 300 would be built on the "Grizzly" medium tank body, essentially a Canadian version of the American M4A1 Sherman medium tank and remainder would be built on chassis of Canadian Ram tank.
All the Sextons were built in Canada at the Montreal Locomotive Works, this facility producing 2,150 SPG's between 1943 and 1945 for both Canadian and British units. The British 8th Army received their first Sexton's in 1943 just in time for the battle of Italy. During the D-day landings, a number of Sextons fired at German shore positions from their landing craft as they approached the beaches, those these had little effect for they were not very accurate from the water. Later, during the Battle of Normandy and the campaign in North Western Europe, the Sextons were assigned to tank battalions to provide a limited anti-aircraft role as well as support in direct fire missions against enemy infantry.
At times, the Sexton would be used as a howitzer for "plunging fire" (arc firing on the enemy) and, other times, as a gun platform for direct fire missions. While working with British artillery units in France, the Sexton was used to attack company-sized units over a series of hills between friendly forces.
The Sexton was a successful design through and through. She could achieve 25mph on paved roads though less than that on off road terrain. Stowage lockers were provided on board for ammunition and personal gear. A canvas cover was afforded the crew in case of bad weather (because of an open turret). Camouflage netting was also provided to help conceal the Sexton from searching enemy aircraft.
They remained in British service up until 1956.