The UK has four nuclear submarines, carrying 12 to 16 missiles, each of which can deliver a number of 100-kiloton warheads to individual targets. The submarines are based at Faslane, near Glasgow. Trident Ploughshares (TP) is a campaign to disarm the UK Trident nuclear weapons system in a non-violent, open, peaceful and fully accountable manner. It began in 1997 when peace activist Angie Zelter wrote to 100 people in 15 countries inviting them to participate. TP now has 226 pledgers (global citizens) from 14 countries, organised into small affinity groups. In addition, there are many supporters who get involved with direct action, who help with legal support, care for those arrested or in prison, press relations, and so on.

TP was officially launched in 1998, shortly after its representatives had written an open letter to the British Prime Minister, Tony Blair, setting out their "nine requests" for the controlled disarmament of British nuclear forces. These requests included:

• that the British Trident submarine system be immediately taken off 24-hour patrols;
• that all British nuclear warheads be removed from their delivery systems and stored separately;
• that Britain should work with its NATO allies for the withdrawal of all tactical nuclear weapons from Europe;
• that the government should commit itself to a timetable for the decommissioning of British nuclear weapons as fast as is feasible and safe, with a target date for completion of 2010 at the latest.

The Prime Minister was told that if a substantial portion of these requests were met, TP would stop its disarmament actions. Otherwise, it would feel bound to pursue its non-violent direct action.

The campaign held its first mass action in August 1998 and others at three monthly intervals since then. In February 1999, two women campaigners managed to board a nuclear submarine and caused damage to its testing equipment. Then in June 1999, three women campaigners succeeded in putting a Trident-related research laboratory out of action. By 2005, TP actions had led to over 2200 arrests, 503 trials and 2184 days in prison.

An important argument of TP is that the UK is not only acting immorally in its policy on nuclear weapons, but also illegally. The grounds for the latter opinion are:

• The Advisory Opinion of the International Court of Justice (ICJ) of July 8th, 1996 "that confirmed the general illegality of modern weapons and concluded that States are under an obligation to bring to a conclusion negotiations on nuclear disarmament in all its aspects".
• The failure of the British Government to implement Article VI of the Nuclear Non-Proliferation Treaty which promised nuclear disarmament by the nuclear powers.

In a number of cases these arguments have been accepted by British judges and juries. In one case the judge stated: "I have to conclude that the [defendants] were justified in thinking that Great Britain in the use of Trident ... could be construed as a threat and as such is an infringement of international and customary law... I have heard nothing which would make it seem to me that the accused acted with criminal intent."