Britain’s nuclear deterrent

Britain has four nuclear-powered Vanguard-class submarines, of which one is always on a three-month patrol. Each submarine carries 16 Trident missiles, each with three 475 kiloton* thermonuclear warheads

UGM-133A Trident D5: Submarine-launched solid-fuelled ballistic missile (SLBM), built by Lockheed Martin

Length: 13m

Weight: 58,500kg 

Range: 12,000km

Accuracy: 90m

Unit cost: $53.6m (£41.3m)

Third stage motor built by United Technologies

Reentry vehicle: MIRV (Multiple Independently Targetable Re-entry Vehicle). Each MIRV is guided by MK 6 stellar-inertial navigation system with GPS updates

First and second stage motors built by Hercules/Thiokol. Use of NEPE-75 propellant and graphite/epoxy composites reduces weight and increases range

Missile compartment 16 missile tubes

Rolls-Royce reactor drives two steam turbines

Crew: 160

Submerged speed: 25 knots

Four Spearfish torpedo tubes

Length: 150m (Jumbo jet to scale)

*Equivalent to 475,000 tons of TNT, Hiroshima bomb was 13-18kT

Sources: Federation of American Scientists, Sandia, 2015 Trident II DoD Budget