In 1955, the Royal Navy created the rank of acting sub-lieutenant, although it had existed intermittently in the world wars. Unlike their substantive counterparts, acting sub-lieutenants are subordinate officers, as they hold their ranks by order and not by commission. Upon passing Fleet Board, acting sub-lieutenants were confirmed as sub-lieutenants and issued commissions backdated to the date when they were appointed acting sub-lieutenants. The rank of acting sub-lieutenant was abolished in the Royal Navy around 1993 but remained in the Royal Naval Reserve until 2013; officers in both the RN and RNR now commission into the rank of Midshipman. The rank of Acting Sub-lieutenant remains in the Royal Navy only within the University Royal Naval Unit where Training Officers enter at this rank.