I can understand how Jeremy Corbyn might not have immediately picked up on the anti-semitic tropes – “globalist” bankers in front of an Illuminati-style eye – present in a mural posted in a Facebook group of which he was a member. Who hasn’t fired off a quick comment on social media without looking too closely into the issue being discussed, or indeed the people discussing it?

Still, the fact that Corbyn could even glance at the image and not see any problems is in itself revealing. Such an image would have jumped out at me.

Why? Because, at the age of 15, one of my classmates at my inner-city London school – one of the cleverer, more articulate and generally nicer classmates – took it upon himself during design and technology to explain how Masonic lodges were part of the global Jewish conspiracy to exploit the world and oppress its peoples. He even had a handy drawing, at the centre of which was the pyramid-shaped all-seeing eye that features so prominently on the mural Corbyn once defended on Facebook.

It was not long after this that another kid in my school asked me whether, as the son of Jew – and during the outbreak of the second intifada in Palestine and Israel – I wasn’t just a little worried about being stabbed. I wasn’t, as it happens, but it seemed like the sort of thing that I should mention to my parents. At which point, they were told by the school's head teacher: “We cannot guarantee your son’s safety”. I left and pretty much never went back.

This is not a sob story, not least because moving schools was one of the best things that happened to me, but it is illustrative of two things. First, you don’t have to be disadvantaged by being Jewish, or physically attacked for it, to be made keenly aware of anti-semitism. And secondly, it is incredibly difficult to disentangle modern anti-semitism from broader politics.

The conflation of left-wing causes with conspiracies about international Jewry is perhaps the most depressing aspect of modern anti-semitism, at least to someone has long identified with those causes far more closely than whatever Jewishness I inherited.

The threads of anti-semitism have long run through the zanier beliefs held on the fringes of the fringes of the left: from banking dynasties controlling our financial services, through arms dealers promoting wars, all the way to Mossad agents blowing up the Twin Towers.

Except, some of those on the fringe of the left have moved into the mainstream following Labour's shift to the left, and brought with them their old bigotry. Views which were tolerated out in the wilds – because they were assumed to be so far from power – are now tolerated, or at least overlooked, at the heart of the party. There is a perception among many British Jews, on both the left and right, that the Chakrabarti report failed to properly address the issue, and that Labour was slow to act on comments by activists such as Jackie Walker.

There is an extra bleak irony to all this. Corbyn and his allies promise to change the structure of capitalism – not just find an accommodation with it, as New Labour did. And yet, as James Bloodworth pointed out on Twitter, the conspiracy theories popular on the fringes of the left ignore structures in favour of blaming individuals:

I think part of the resurgence in left antisemitism derives from a wider left retreat from materialism. Notice how capitalism is rarely analysed nowadays as a system of relations and instead the focus is on the power of the *bad people* - bankers, newspaper proprietors etc... — James Bloodworth (@J_Bloodworth) March 24, 2018

This idea that the problem with the world is that dastardly people control it - as opposed to the Marxist idea (I'm not a Marxist but it's useful) that they're mere caretakers - does imo lend itself more easily to antisemitism... — James Bloodworth (@J_Bloodworth) March 24, 2018

The notion of a nefarious 'establishment' controlling things behind the scenes mirrors the classic antisemitic trope, and it doesn't take much for, say, 'the bankers' to be replaced by 'the Zionists' and then 'the Jews'... — James Bloodworth (@J_Bloodworth) March 24, 2018

Socialism – the ideology which attracted me to politics in my teens – is about reforming the structure of society. It is not about finding people, or groups, to hold responsible for all the evils in the world. And yet, much of the campaigning from today’s left seems driven by personal animosity; taking in everyone from Tory leaders to insufficiently left-wing Labour MPs.

Ultimately, that is even more depressing than Labour’s inability to deal with those in its ranks who have a problem with Jews.