ITV would very much like it if viewers used its "#leadersdebate" Twitter hashtag when talking about tonight's unprecedented seven-way live debate between the UK's party leaders. Unfortunately, a lot of people are tweeting under the #massdebate hashtag instead. They seem to believe that the debate will be a rather sprawling affair, with the leaders of the Conservatives, Labour, Liberal Democrats, UKIP, Greens, the SNP and Plaid Cymru all going head-to-head over two hours.