The Rifle, Anti Tank, .55inch, was issued to British infantry units from 1934 onwards. The head of the design team, Capt Henry Boys, Assistant Superintendent of Design at the Royal Small Arms Factory, Enfield drew inspiration from a Polish design, and redesigned the round to provide greater penetration (23.2mm at 100 yards) utilising a .55 calibre.
Boys died just before the weapon was accepted into service and it was named "Boys" in his honour.
Some early Boys were used by the covering party in landing craft during the Bruneval raid.
The weapon was fed from a top loading magazine with off set sights and single monopod at the front. In mid-1942, a lighter and shorter version was developed for airborne forces. The barrel was shortened and the muzzle break was removed and some parts replaced with aluminum alternatives. A Bren style bipod was also added. However, performance was affected by the changes.
In 1943 the Boys was replaced in airborne use by the PIAT.