1912 – 1938
Nos. 3 and 4, are ammunition carriers. No. 3 takes the first supply of ammunition to the gun, assisted by No. 4, and arranges that the spare parts wallet is brought up to the gun position. No. 4 takes the ammunition from the limber to No. 3, when a further supply is required, and also the condenser complete and half-filled with water. No. 3 is responsible that the condenser reaches the gun position before there is any chance of the water boiling. No. 4 places his own rifle and those of Nos. 1, 2, and 3, in the limber.
1939 – 1942
The No. 4 is identified as a ‘spare man’ and carried additional ammunition liners and a Pickaxe, or potentially a Shovel.
1943 (Airlanding)
1943 to 1968
During this period, after the Universal Carrier was introduced, and the Land Rover then used, the role of the No. 4 was undertaken by the Driver.