4. For the purpose of these Rules, the expression “war service” means
(a)service in any of His Majesty's forces or the nursing and auxiliary services thereof;
(b)service in the Merchant Navy, including the sea fishing service, the pilotage and light vessel services, or as a salvage worker;
(c)full time service in the civil defence services (including the National Fire Service), the Royal Observer Corps, the Police War Reserve, the nursing and first aid services, and the Women's Land Army;
(d)any full time employment into which a person entered by direction of the Minister of Labour and National Service;
(e)detention by the enemy as a prisoner, military or civil, in any enemy or enemy-occupied country or internment in any enemy or enemy-occupied or neutral country in consequence of the war;
(f)such other employment as the Minister, with the consent of the Treasury, approves in writing;
such service, employment, detention or internment being on or after the 26th May, 1939, but not including any voluntary extension of war service or voluntary enlistment after the cessation of hostilities otherwise than with the consent of the employer in whose service the person was, both at the time of the consent and immediately before the commencement of his war service.