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The Driver ( Dvr ) is the military rank used in the British Army and other Commonwealth army units. It's the equivalent of a personal rank.
This rank was originally used at Royal Artillery for those who piloted a horse team that drew its weapon. It was removed after the First World War (when all Royal Artillerymen of the lowest rank redesigned as a shooter). It is also used in Royal Australian Artillery and Royal Canadian Artillery.
It is also used by all private correspondents of the Royal Army Service Corps and then Royal Corps of Transport, no matter what their trade. When the RCT was merged to form the Royal Logistic Corps in 1993, the rank finally vanished from the British Army.
Source of the article : Wikipedia