A significant development in the race for the Labour leadership this afternoon after the GMB union announced that it will be backing Ed Miliband. The GMB is one of "the big three" unions (the others are Unite and Unison) and their endorsement will give the younger Miliband some much-needed momentum.
Since the abolition of the trade union block vote under John Smith, members have been free to vote as they wish, but in practice a significant number of the GMB's 700,000 members will back Miliband. In the 2007 deputy Labour leadership election, about 40-50 per cent of trade unionists voted for the candidate recommended by their union's leadership.
For those unfamiliar with the intricacies of Labour's electoral college, the trade unions hold a third of the vote in the leadership election.