The first of his kind? Frank Field has resigned the Labour whip citing the party’s “toleration of antisemitism” and a “culture of nastiness, bullying and imtidiation that [the leadership] has allowed to grow unchecked”.

As I wrote last week, the number of Labour MPs who are contemplating a split is growing, and it is a matter of if, not when. But I wouldn’t see Field as the first (or, given that John Woodcock has already walked out of the Labour party, the second) of his kind. Just as he has been throughout much of his career, Field is a lone wolf and something of an exception among even those Labour MPs planning to leave the party, for a variety of reasons.

As party activists and Corbyn-friendly commentators are pointing out that the Birkenhead MP was facing the prospect of deselection after rebelling on a series of knife-edge votes. Of the five pro-Leave MPs to break the whip, Field, Kate Hoey and Graham Stringer are all facing the prospect of deselection, while Kelvin Hopkins is in any case suspended following allegations of sexual harassment.

That puts that five in a very different position to most Labour MPs thinking about a split. For one reason, what binds many Labour MPs with extreme doubts about Jeremy Corbyn into the party is the hope that they can, in the words of one MP who described herself as “increasingly disconnected” from the Labour party, “soften or perhaps even stop Brexit”. A lot of that group regard talk of a new party as actively unhelpful at this stage as it distracts from the real business of preserving the United Kingdom’s single market membership, while others see it as the “only way you can square staying in the party morally”.

As far as Field is concerned, he wants Brexit to happen and for it to be as big a breach with the European Union as possible. The party’s position is already too soft for him and if it changes (which is unlikely but not impossible) it will become less congenial to Brexiteers like Field, not more.

Field has also been at odds with his local party for some time – in March of this year he fell out with his constituency party sufficiently badly that he has ceased to attend general committee meetings pending an apology (which has not, of yet, been forthcoming). His local party has also been at the epicentre of Labour’s ongoing row over antisemitism in the ranks, with the Birkenhead Labour party voting to turn down diversity training from the Jewish Labour Movement due to its connections with the Israeli government and (entirely non-existent) links to the Islamic State.

So while no-one could fairly claim that nothing untoward was going on in the Labour party in general and in Birkenhead constituency in particular, it is true to say that there have been problems in that part of the world for some time, and it is hard to see what has materially changed, other than Field’s position following a series of contentious Brexit votes.

Equally importantly, Field is leaving open the possibility of rejoining if his conditions are met. Now it is highly unlikely those conditions will be met. But when other Labour MPs quit the whip – which they will – they won’t do so in a way that leaves a return to the party under Corbyn alive as an option.

But his exit does have one important wider consequence: there is a perception within the party, and not just among Corbynites, that when John Woodcock quit the party he did so largely to escape legitimate claims of sexual harrassment (Woodcock denies the allegations). That made some Labour MPs reluctant to follow. Field’s most important role in what happens next to Labour may have been in changing the perception of those who walk away, among Corbynsceptics at least.

Update: This article was amended on 31 August to correct an editing error that suggested that any links between JLM and both the Israeli government and Isis were “entirely non-existent”. That phrase should have referred specifically only to Isis.