Watching Harriet Harman being interviewed by Laura Kuenssberg on Newsnight earlier this week was a strange experience. I felt as if I’d entered a political twilight zone where nothing was quite as it seemed. Was the deputy leader of the Labour party really saying these things? I knew she was, but it seemed so miscalculated — so unwise — it was as if Harman’s body had been taken over by someone else. A mischievous political demon, perhaps. Or Lynton Crosby. The entire interview was like a nine-minute party political broadcast for the Conservative party.

By my count, Kuenssberg gave Harman five chances to admit that it had been a mistake for the National Council of Civil Liberties to grant ‘affiliate’ status to the Paedophile Information Exchange, a notorious lobby group that campaigned for the age of consent to be lowered to the age of four, and five times she refused. Why?

Harman’s argument was that, as a matter of policy, the NCCL didn’t bother to vet any group or individual that applied to join. Indeed, there doesn’t appear to have been a formal application process. Any group willing to pay the membership fee could ‘affiliate’ with the NCCL. As the legal officer, she had no say in the matter.

But as Kuenssberg pointed out, the NCCL could have expelled the PIE once it had come to light that a group actively campaigning to legalise sex between adults and children had joined the organisation. And yet it chose not to. Wasn’t that a mistake?

Even if that wasn’t possible — Harman muttered something about policy being dictated by the ‘annual general meeting’ — couldn’t she have resigned? I like to think that if I discovered an organisation I was helping to run had been infiltrated by paedophiles, and there was no mechanism for getting rid of them, I’d resign. But Harman didn’t. Wasn’t that a mistake?

Finally, while Harman was the NCCL’s legal officer, she campaigned for sentences against convicted paedophiles to be ‘reduced’ and argued that people found in possession of pictures of naked children should only be prosecuted if it could be proved that the children in question had been ‘harmed’. Wasn’t that a ‘mistake’, given that her salary was being paid in part by a group of active paedophiles?

No, no, five times no. Je ne regrette rien.

To be fair, Harman did express ‘regret’ the following day, by which time it had dawned on her (I imagine) that this interview was an unmitigated disaster. But why was she so unapologetic in the first place? What was she thinking?

It wasn’t just me who was astonished by her performance on Newsnight. A few minutes afterwards, I got a call from a senior BBC news producer who was equally gobsmacked. And this was someone who was broadly sympathetic to the Labour deputy leader. ‘Why didn’t she just admit it was a mistake, apologise, and draw a line under the story?’ she said. ‘It was one of the most bizarre interviews I’ve ever seen.’

The best explanation we could come up with is that her judgment was clouded by her visceral hatred of the Daily Mail, which had been taunting Harman, along with her husband Jack Dromey and colleague Patricia Hewitt, with successive front-page stories on the subject. During the Newsnight interview, and the following day, Harman tried to turn the tables on the Mail, demanding that it should apologise to her and accusing it of hypocrisy when it comes to the sexualisation of children. To prove her point, she even tweeted a picture that had run in the Mail of three young girls in bikinis.

But this just compounded the error. Was Harman really suggesting that running a picture of a scantily clad 12-year-old girl was morally equivalent to the activities of a group of active paedophiles? If so, her internal compass is even more skewwhiff than the Newsnight interview suggested. It’s as though she has a moral blind spot, cannot see the full horror of the group the NCCL was linked with. Maybe some part of her won’t allow her to see it because she knows her conscience wouldn’t be able to cope.

By the time this article appears, Harman may well have issued a full apology. I hope she has because I’m genuinely concerned for her mental health. If she remains unrepentant and continues to shoot the messenger, I fear she may go completely mad. Whatever happens, she should steer well clear of Newsnight for the foreseeable future.