Britain has been a nuclear weapons power since 1952 when an atomic device was successfully detonated in the Monte Bello Islands in Australia in October of that year. No British Prime Minister in 55 years has seriously considered giving up the deterrent.

Q What does the deterrent consist of today?

A It’s made up of four Vanguard class nuclear-powered submarines, each with a capacity to carry 16 Trident D5 missiles armed with 12 warheads. But the Government has stated that no submarine goes out on patrol with more than 48 warheads.

Q How powerful is Trident?

A The D5 missile has a range of 4,000 nautical miles and an accuracy, so it is claimed, which can be measured in metres. Each warhead has eight times the explosive power of the atomic bomb dropped on Hiroshima in 1945 which killed more than 140,000 people.

Q Is Trident Britain’s only nuclear weapon?

A Yes, all the tactical nuclear weapons, such as the RAF’s WE177 free-fall nuclear bomb, and atomic depth charges deployed with Royal Navy warships, were scrapped by 1998. The number of operationally available Trident warheads stockpiled by Britain is to be reduced to fewer than 160.

Q How long has Britain’s strategic deterrent been deployed in submarines?

A Since 1968 when the first Resolution class submarine, armed with Polaris ballistic missiles, went on patrol. Since then, the Royal Navy has completed 300 deterrent patrols, with the Vanguard class Trident boats beginning to take over the round-the-clock missions from 1994.

Q Is Trident a truly independent weapon or does the United States have a veto on its use?

A The Prime Minister is the only person who can authorise a launch in anger of a Trident missile, and Washington has no controlling system to prevent it, although it is difficult to envisage a scenario in which Britain would be about to resort to nuclear weapons without her American ally being involved in the same international crisis.

Q What were the options facing the Government in considering a replacement for the present Trident system?

A An upgraded version of Trident D5, now being developed by the US, to be installed in a new submarine (the chosen option); an adapted Trident D5 fitted to three large surface warships; 20 large aircraft equipped with cruise missiles; ground-based Trident missiles installed in two silo fields.

Q Why was the submarine option considered favourable?

A Because after years of operational experience with Polaris and then Trident, the submarine was judged to be the least vulnerable system.

Q What is the rationale for maintaining a nuclear deterrent in the post-Cold War world?

A Britain’s nuclear weapon was not designed for use in a military conflict but to deter an enemy from launching a nuclear attack on this country. Although the threat of a mass nuclear attack by the Soviet Union vanished when the Soviet empire collapsed, the same argument is still being deployed. In an increasingly unpredictable world in which numerous countries might try to join the nuclear club, Trident in its new form is intended to remain this country’s ultimate insurance policy.

Q If the Government gives the go ahead for American anti-missile interceptors to be based in this country as part of the so-called “Son of Star Wars” programme, why do we need to have Trident at all?

A The Government argues that missile defence could only ever be complementary to having a deterrent and could never replace it.

Q Timeline for the new Trident?

A The Trident replacement will be needed by 2022, the Government says, when the current submarines will go out of service. A decision is required now, it is argued, to ensure there is no break in the nuclear patrols. It’s estimated it will take up to 17 years to design and build the submarines, and after yesterday’s Commons vote, the Ministry of Defence will begin discussions with industry on a conceptual design for the new boat. A decision on a new Trident warhead which will be designed at the Atomic Weapons Establishment in Aldermaston, Berkshire, will not be needed until the next Parliament.

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