An extensive armaments depot at the head of the Rosneath Peninsula in Argyll & Bute, RNAD Coulport is responsible for the storage, processing, maintenance and issue of the UK's ultimate deterrent, the submarine-borne Trident weapon system with its nuclear warheads. Constructed between 1963 and 1968, the base has at its core sixteen nuclear weapons storage bunkers built on a ridge overlooking Loch Long. Initially these were constructed to store Polaris missiles, but were subsequently re-used for Trident from the 1990s. Expanded between 1982 and 1995 at a cost estimated at £1.9 billion, the base now covers an area of 1.5 sq. miles (3.8 sq km) and includes two main jetties on Loch Long, together with numerous workshops, support and administrative buildings. One of the jetties is covered, allowing missiles and warheads to be loaded and unloaded unobserved. Submarines sail the short distance from HM Naval Base Clyde in the Gare Loch to Coulport to be armed. Coulport is also responsible for other submarine-borne weaponry, such as Spearfish torpedoes and the Tomahawk land-attack cruise missiles fired by the Navy's Astute-class submarines.
The approach from Garelochhead is by a grand but constantly security-patrolled public highway which offers fine views over the head of the Gare Loch and HM Naval Base Clyde. The Trident missiles are drawn from a pool jointly owned by the USA and UK, and tend to be serviced by the US Navy Strategic Weapons Facility Atlantic at Kings Bay in Georgia. However, the UK-owned warheads are regularly transported by road to the Atomic Weapons Establishment at Aldermaston in Berkshire (England) for maintenance, the long transporters making use of gates to cross the roundabouts on the approach road to the Coulport facility.