Prior to the introduction of the Special Duties List in 1956, some senior ratings were selected for promotion to Warrant Officer on the Branch List, with subsequent possible promotion ( from 1864 ) to Commissioned Warrant Officer; from 1946, officer rank was achieved by commission rather than by warrant.
12.
Petty officers and chief petty officers could, with the approval of their commanding officer, become a CW candidate ( an'SD candidate') and such supply branch senior ratings were similarly specially reported on with a view to promotion to officer, generally between the ages of 28 and 35, though most were in their early 30s when promoted to acting sub-lieutenant on the Special Duties List.
