The Trident missile is a submarine-launched ballistic missile (SLBM) equipped with multiple independently-targetable reentry vehicle (MIRV). The Fleet Ballistic Missile (FBM) is armed with nuclear warheads and is launched from nuclear-powered ballistic missile submarines (SSBNs). Trident missiles are carried by fourteen active US Navy Ohio class submarines, with U.S. warheads, and four Royal Navy Vanguard class submarines, with British warheads. The original prime contractor and developer of the missile was Lockheed Martin Space Systems.

In 2006, the government’s White Paper on Trident Replacement estimated a cost of £11-14 billion for new nuclear weapons submarines. But recently the government published a progress report which shows that the cost of the subs is actually likely to be £25-26 billion. The total cost of the whole programme, including lifetime costs, will exceed £100 billion. At a time of massive government spending cuts, many people believe this to be an appalling waste of tax payers' money.

Cut Trident
http://en.wikipedia.org/wiki/Trident_(missile)