The High Court giveth, and the Court of Appeal taketh away. The Labour Party has won its appeal against the ruling that party members who joined after the January 2016 “freeze date” introduced by the party’s ruling national executive committee, meaning that around 150,000 party members will not be able to vote in the leadership election.

What does it mean in terms of the ongoing battle for the party leadership? We only have one poll of the contest so far, taken when both Angela Eagle and Owen Smith were still possible challengers to Corbyn and the majority of Labour members couldn’t pick Smith out of a line-up. In that poll, Corbyn led Smith by 22 points.

Since then, a lot has happened. More than 150,000 people have paid £25 to vote in the Labour leadership race. By my estimation, having spoken to more local party officials than is healthy, around a third of the £25ers are party members who fell foul of the cut-off date, but the rest are the great “known unknowns” of the contest. The GMB and Unison, following consultative ballots, have endorsed Owen Smith and Jeremy Corbyn, respectively. Pro-Corbyn candidates swept the board among the membership section in the party’s NEC elections. And 275 constituency Labour parties have made supporting nominations, on which metric Corbyn leads Smith by 234 to 41.

Crucially, those nominations have only included the votes of party members who joined before the 2016 cut-off. It is hard to draw up a metric by which Corbyn is not winning. He is winning in constituency parties that nominate via all-members-meetings. He is winning in constituency parties that nominate via delegates. He is winning in held seats. He is winning in Tory seats. He is winning in constituencies that nominated Yvette Cooper, Liz Kendall, and especially those that nominated Andy Burnham. There is no part of the Labour party where he is not winning, though he is doing slightly less well in Scotland and London, and very well in Merseyside.

So, to be frank, as far as members are concerned, the ruling feels unlikely to make much difference to the outcome, although it is possible that a tide of trade unionists and £25ers will sweep Corbyn out. My impression, from talking to new members, is although they were comfortable joining a party led by Corbyn, it is the European referendum that is behind the bulk of the surge.

Europe is the only issue which Corbyn is at variance with the bulk of members, although as I’ve written before, he has done an astute job of managing that divide for the most part. But the open question of how far to contest the referendum and his call to invoke Article 50 “now” may make him more vulnerable among these new members than the old.

(Personally, I doubt it. Most of Labour’s “pro-Europeans” are only pro-European in the same sense most Britons are Christian: they’re broadly supportive, they’re glad it’s there, but it will always come far down the list of policy priorities for most. But it represents a better shot for Smith than betting on pre-January members in my view.)

Barring an turnaround at the Supreme Court, the verdict almost certainly means that Corbyn will win and win well among Labour party members in September. But it will change Labour’s trajectory after his victory. The taboo on changing the rules to suit yourself has always been fairly weak in the Labour party, but it has been well and truly broken now.

But it will likely deprive Labour’s Corbynsceptics of the myth that has now become mainstream: that Corbyn’s victory was the result of “other people”, that his opponents lost because of the Greens, etc. My guess, if the freeze date had been overturned, his opponents would have returned to that idea, no matter how big or how small the margin of victory. That might mean a change of approach for the Corbynsceptics after he wins. Currently ascendant is what one politician described as the "we have to call him a c**t every day until he f****s off" school of thought. Some are already planning for another challenge early in the New Year. It may be that defeat under these circumstances breaks the back of that tendency, at least for now.