The Gang of Four were four British Labour MPs who set up the Social Democratic Party (SDP) on 26th March 1981.
They were Roy Jenkins (a former Labour cabinet member, David Owen, William Rogers and Shirley Williams. They putlished a 12-point document covering elections, education and international co-operation.
They described themselves as centre-left party and were the first to be run in Britain with a one-member one-vote system for policies and selection. (The other parties give block votes to trade unions and other organisations.)
In the Autumn of 1981, the party joined forces with the Liberal Party lead by David Steel to create the SDP-Liberal alliance. They enjoyed some increasing support through the 1980's, but by the 1987 general election the Alliance was weakened by high Labour support.
After the election, David Steel proposed an official merger with the SDP and while most of the SDP's membership voted in favour of the merger, David Owen remained adamantly opposed to it. He pledged to fight the now new Social and Liberal Democrat Party (SLD).
But by 1990, the party had lost a great deal of credibility and support and the SDP was folded.
As of now, the remnants of the party are simply the Liberal party, who often poll over 20% of the votes, but due to the UK's first past the post electoral system, rarely get more than about 10% of the seats in the House of Commons.