I can’t claim that I’ve been singing it, but each time I think of it, it makes me smile. You can join in if you like. Hum to yourself the tune of the Crystals’ pop classic, Da Doo Ron Ron. Then ditch the original lyric and replace it with this one: “The Jews, Len, Ken, Ken, the Jews, Len, Ken.”

Credit for that belongs to my fellow journalist, Hugo Rifkind. He tweeted it after I’d written a piece about Len McCluskey, Ken Loach and Ken Livingstone  —  all of whom had weighed in on the subject of Jews and antisemitism during a single day at the Labour party conference.

JC readers will know all about that, I’m sure. They won’t need to hear again the arguments I made in the Guardian. That it was almost comic to hear three non-Jewish men insist that because they had never experienced any anti-Jewish racism on the left, then it clearly did not exist. That the left was meant to understand that racism is best defined by those who experience it, yet oddly many leftists felt comfortable making an exception for antisemitism, believing that they, rather than Jews, were best placed to say what was — and what wasn’t — prejudice against Jews. And that it was itself a long-established staple of antisemitic discourse to suggest — as Len and the Kens had — that complaints of antisemitism were invented or exaggerated in order to further some hidden agenda.

But as I say, JC readers know all that already. It will be wearily familiar, with emphasis on the weary. Which is why I don’t want to go back over that same old ground. Instead, I want to talk about the effect these now persistent rows about antisemitism are having on British Jews, especially those who have long identified with Labour or the wider centre-left.

I was in Brighton when this latest series of rows erupted and my heart sank when I heard it had kicked off all over again. I was, of course, saddened first by the immediate flashpoint: talk of Holocaust denial at a fringe meeting, as elsewhere an ultra-left faction handed out leaflets claiming an ideological affinity between Zionists and Nazis, between those German Jews who had been seeking a homeland and those who craved their murder — between those who yearned to save Jewish life and those who craved Jewish death.

But I was also glum about the effect this would have. Brighton had the atmosphere of a victory party. Labour supporters were in high, if not ecstatic, spirits. Many of them feel what can only be described as love for Jeremy Corbyn; they believe he is leading them into government and a bright new future.

And here to spoil the party was yet another row about antisemitism. Make no mistake: that’s not the fault of Jews, but of Jew-haters. But it was hard not to feel that, once again, we had become the cloud on their horizon.

For the people who venerate Corbyn as a kind of secular saint — and one delegate was holding aloft a portrait of the leader, ringed by twinkling lights, like a Catholic icon — there is only one objection that keeps surfacing and, they feel, it’s the Jews who keep making it.

This troubles me. There was lots of talk in Brighton of the “bagel belt”, the handful of north London seats that stubbornly refused to fall to Labour in June: had those seats backed Corbyn, Theresa May would have been denied even her narrow majority with the DUP. How long before the view forms that Jeremy would be in Number 10 now if it hadn’t been for you know who?

But the other source of my glumness was the sheer waste of energy. I watched as bright, committed Jewish women and men on the left had to sigh, gird themselves and — yet again — begin the thankless work of explaining that, no, Jews do not brand “any and all criticism” of Israel as antisemitic; that, on the contrary, many Jews and Zionists make such criticisms of Israel all the time; that their only objection is when that criticism relies on age-old anti-Jewish stereotypes… and on and on.

I know many of those Jewish Labourites and I know they would prefer to be talking about almost anything else. Housing or Brexit or the NHS. But, instead, they are dragged back to the cesspit of antisemitism by a bigoted Facebook post or a stupid remark by an ageing Labour bigwig.

And it keeps us from having the conversations among ourselves that we need to have — including about Israel’s conduct today and the occupation which endures, seemingly forever. We need to face that painful reality. But every time a Loach or a McCluskey sounds off, we find ourselves defending our history and, in the process, closing ranks, even circling the wagons.

Put simply, these now-perennial rows about antisemitism are bad for Labour and bad for us. I long for the day that Labour deals with this problem properly — for their sake and for ours.

Jonathan Freedland is a Guardian columnist. His latest book (as Sam Bourne) is ‘To Kill the President’ (HarperCollins)