The former Labour MP Chris Mullin did Jeremy Corbyn no favours this week when, by way of proving how little antisemitism there is in the Labour Party, he posted an antisemitic tweet. 

“Sorry to see Jewish leaders ganging up on Corbyn,” he wrote. “Suspect it has more to do with criticism of Israel than antisemitism.” 

Ganging up on!  The idea of the Board of Deputies and the Jewish Leadership Council turning up mob-handed to rough up the leader of a major political party is gloriously absurd given what a small, moderate, not to say timorous force in British society Jews are. 

But an accusation can be simultaneously preposterous and malign. In his brief tweet Mullins managed to pack in accusations of Jewish conspiracy, intimidation, bad-faith, duplicity, self-pity and self-interest, just to draw the line there. 

The monotonous and insulting libel, that all that drives complaints of antisemitism is the desire to silence criticism of Israel, has been the left’s get-out-of-jail-free card for years and explains Corbyn’s apparent disdain whenever the charge of antisemitism in his party is levelled. The charge itself, in the reasoning of the left, is crooked.

As for the claim made by Corbyn’s supporters that he doesn’t have an antisemitic bone in his body, that is neither here nor there if he doesn’t believe that antisemitism, as a recognisable racism, exists. Only witness the difficulty he has always experienced just saying “antisemitism”.  In the parlance of the left, the assertion “I am not a racist” does not mean “I am not an antisemite”.

If there is a change in Corbyn’s normally guarded vocabulary this week, optimists hope it is because even he knows a line has been crossed. Behind every refutation of previous wrong-doing in relation to Jews — his hanging out with representatives of Hamas, his association with rabid Jew-haters and Holocaust deniers, his sharing social media platforms with medievalists who accuse Jews of harvesting the organs of their enemies — there has always been a silent contempt for Jewish motivation. All right, maybe he didn’t check the credentials of his associates as carefully as he should have, but who are Jews with their imperialist Zionist sympathies to point the finger.

But this latest affair of the mural is another ball game. Here, without the distractions of Zionism, is the old, naked Jew-hating thing. The mural which Corbyn went out of his way to champion in 2012 — visiting the artist’s Facebook page and offering his support against the local council’s decision to remove it — shows a conspiracy of financiers, most of them undisguisedly Jewish in the mode once favoured by the Nazi propagandist Julius Streicher, playing a pitiless game of Monopoly on a board supported by the naked backs of the world’s oppressed.

On a second look, years later, Corbyn accepts its antisemitic intent. But he still reverts to his trusted “inadvertence defence”. He hadn’t “looked closely” at the image. 

 An ill-judged gambit at any time — for what is a professional politician doing lending his name to a cause he doesn’t bother to investigate? — inadvertence beggars credibility in this instance, so unmistakable is the artist’s meaning. Never mind looking closely: to throw the most perfunctory glance at this mural is to be struck by the familiarity of its caricature of Jews conspiring to defraud and exploit. 

Corbyn’s insistence that he didn’t see any of this incriminates him all ways. And in the end there is only one conclusion we can reach: if he saw nothing exceptionally offensive in this mural it can only be because it mirrored an image of the Jew as bloodsucker he was already carrying in his head.  

In order to calm the storm, Corbyn has tried to put blood into his latest expressions of regret by owning up at last to what he calls “pockets of antisemitism” in his party — “more than a few bad apples” he has since expanded, as though a few bad apples was ever anyone’s reading of the systemic, ideological problem at the heart of Labour. 

But yet again, the language of apology falls short of the offence. “Pockets” not only minimises the degree and reach of prejudice on show, it distances Corbyn himself from it. 

“You are the pocket, Mr Corbyn,” said a placard at Monday’s rally. After years of contemptuous denials, it is hard to resist the logic of that. A predilection for the company of antisemites isn’t, after all, a matter of chance. There comes a time when you have to face the possibility that the thing you flirt with, you are.