Take Labour leadership polls with a pinch of salt – we still have no real way of knowing who’ll win

Not only do they exclude registered supporters and members of affiliated groups, we don’t yet know what the full line-up of contenders will be

The YouGov poll may show Keir Starmer with a commanding lead over potential rivals to succeed Corbyn, but can it be trusted? (PA)

Party leadership contests are notoriously difficult for political correspondents to get a handle on.

In the olden days, when Tory leaders were picked by MPs and Labour had a complex college system in which trade unions wielded bloc votes, it was easy to take soundings inside the Westminster bubble and form a shrewd judgement on who was in line for the top job.

But with democratisation of the process in all the major parties, decision-making power now lies in the hands of the membership – and also in Labour’s case with “registered supporters” and members of affiliated unions and groups like the Fabians or the Jewish Labour Movement.