The first shipments of shells, rockets, mines, flares and small arms ammo arrived early in 1968 with shipments arriving in lorry convoys as well as rail. The majority of lorry convoys took place at night not to cause local road disruption, along with the freight trains, as they had to fit with BR timetables. In the early 1960s Severn Tunnel locomotive depot was not far away and steam locomotive no. 2231 was allocated as a permanent locomotive for shunting etc. at Caerwent (Dinham). This locomotive had a special spark arrestor fitted in the smoke box at Swindon to avoid sparks being blown and causing a fire hazard. The driver and fireman were forbidden to smoke at any time whilst inside the perimeter gate. Maintenance facilities were added in 1971.