The gun was fitted predominantly to the Centurion tank, first seeing action in 1950 with British Army units during the
Korean War and
Suez Crisis (1956). In 1956, detailed intelligence on the then-new Soviet T-54A main battle tank was obtained by the British military, after Hungarian rebels drove to the British embassy in
Budapest, during the
Hungarian Revolution of 1956. Analysis of the T-54's armour suggested that the 20 pounder would be ineffective at penetrating the latest Soviet armour. The 100 mm gun wielded by the T-54 was also assessed. The Centurion's earliest combat experiences and intelligence on Soviet armour and tank guns led to development of the 105 mm L7 tank gun, which was designed to fit specifically into the turret mountings of the 20 pounder, facilitating retrofitting to existing tanks. During the development of its successor, the 20 pounder continued in front-line service and was even trialed in other fighting vehicles. One was fitted to a Swiss pre-production
Panzer 58, replacing a domestic 90 mm Kanone 1948 gun. (However, the Panzer 58 was later equipped with the 105 mm L7.) Between 1968 and 1971, Mk 5/1 Centurions of the Australian Army, equipped with the original 20 pounder, saw action during the
Vietnam War. In the context of counterinsurgency operations in
South Vietnam, the 84 mm ammunition of the 20 pounder was considered suitable for the armoured fire support role. (
North Vietnamese tanks did not operate in South Vietnam until later stages of the war.) ==Performance==