The 2007 Labour Party leadership election was formally triggered on 10 May 2007 by the resignation of Tony Blair, Labour Leader since the previous leadership contest on 21 July 1994. At the same time that Blair resigned, John Prescott resigned as Deputy Leader, triggering a concurrent election for the deputy leadership. Informal campaigning had been ongoing ever since Blair announced in 2004 …

https://en.wikipedia.org/wiki/2007_Labour_Party_leadership_election_(UK)