The position of leader of the Labour Party was formally established in 1922 and Jeremy Corbyn became the fourteenth individual, excluding temporary acting leaders, to hold that office when he won the leadership election of 2015. Of the previous 13 holders, six – Ramsay MacDonald (1922– 31) Clement Attlee (1935– 55), Harold Wilson (1963– 76), James Callaghan (1976– 80), Tony Blair (1994– 2007) and Gordon Brown (2007– 10) – would also serve as Labour prime ministers. Of the seven who led the Labour Party but failed to serve as prime minister, two – Hugh Gaitskell (1955– 63) and John Smith (1992– 94) – were Labour leaders of the opposition who held a lead in the opinion polls and seemed on course to become prime minister, only to pass away suddenly. The remaining five who failed to serve as prime minister were Arthur Henderson (1931– 32), George Lansbury (1932– 35), Michael Foot (1980– 83), Neil Kinnock (1983– 92) and Ed Miliband (2010– 15).

Miliband joined the list of Labour Party leaders who failed to become prime minister because of the poor performance of the party in the general election of 2015, which prompted his resignation. When Miliband acquired the leadership in September 2010, the Labour Party had recently lost the general election of May 2010 on the back of securing 8,606,518 votes and a 29.0 per cent vote share, which resulted in them securing 258 parliamentary seats, leaving them in opposition to a Conservative– Liberal Democrat coalition (Kavanagh & Cowley 2010: 350– 51). The failure of the Miliband opposition era was confirmed at the general election of 2015, when their parliamentary representation went down from 258 to 232 seats (-26), even if in terms of votes cast and vote share there was evidence of a limited recovery – they secured 9,347,273 votes on a 30.4 per cent vote share (Cowley & Kavanagh 2015: 433; on the Miliband opposition era, see Bale 2015, Goes 2016).

Miliband had won the leadership of the Labour Party via the Electoral College system of leadership selection. The Electoral College was a one-member-one-vote system, but it had a tripartite structure with one-third weight given to each of the following: (a) the PLP plus Labour members of the European Parliament; (b) individual Labour Party members from constituency associations; and (c) members of trade unions and affiliated societies.