Let me start by confessing that Diane Abbott made my heart sink long before she opened her mouth on BBC Question Time last week – and she has made it plumb the depths since.

The confected row over the shadow home secretary’s “treatment” on the show showcases all that is rotten about the current Labour leadership, and the warped priorities of deeply unpleasant Momentum activists behind it.

Neither Abbott nor I were thrilled to find ourselves sitting in close proximity on the train north for the recording of the show: nothing personal on my part, but less than ideal for rehearsing lines or taking sensitive telephone calls.

I briefly considered moving to another seat but didn’t want to be rude. There’s an unwritten rule on Question Time that however great their political differences, panellists are nice to each other off-air. After all, we’re all in it together in that bear pit. So I stayed put and went out of my way to be friendly.

By contrast, the shadow home secretary could not be bothered with the most basic civilities. In 15 years at Westminster I’ve rarely seen such bad manners – but that is by the by. Politicians are entitled to be rude, and express their distaste at sitting near me.

It is the faux allegations of racism and sexism towards Abbott on the show that really depress me - and tell us so much about the poisonous culture in sections of the Labour party.

At the heart of the controversy is a bizarre claim that during rehearsals with the audience, presenter Fiona Bruce made an off-the-cuff remark about Abbott’s fling with Jeremy Corbyn decades ago.

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I can’t be certain that she didn’t, because I wasn’t in earshot. Nor was Abbott, who is relying on hearsay. However, it seems vanishingly unlikely that the ultra-professional presenter of the Antiques Roadshow would have indulged in any type of inappropriate banter in such an environment moments before the cameras rolled.

The second allegation is that the Question Time team deliberately “whipped up” the audience against Abbott before the show aired. This further stretches credulity. Such an exercise was entirely unnecessary. Labour’s incoherent Brexit policy is enough to challenge even the most loyal Labour supporters. The party leader’s childish refusal to engage in talks with Theresa May about Brexit unless she rules out “no deal” is a further gift and would have been quite enough to set off the audience. A third allegation concerns my suggestion on the show that Labour is “way behind” the Tories in the polls.

As this entirely confected row has dragged on, some Labour type with far too much time on their hands has worked out that Abbott was interrupted significantly more often than other panellists. The best explanation her supporters can come up with for this is racism, sexism or political bias on the part of the BBC.

The truth is much simpler: she talks agonisingly slowly, opening up plenty of opportunities for intervention. And once she starts, she never stops. If we all waited politely for her to finish, nobody else would ever speak.

That the Mirror’s Kevin Maguire should declare without any apparent irony that all this entirely trivial row “puts the public service broadcaster in crisis,” shows just how badly the Labour party has lost its way.

Perhaps if they spent less time pursuing trumped up grievances, and more time coming up with credible policies, they would have some chance of ousting the Tories.

best o