You can see why Boris Johnson’s carers have chosen to mothball him in recent weeks. His decline has been almost total. Johnson never did much care for the past or the future. Every day has always been a tabula rasa, one on which he was free to reinvent himself as he pleased without being bound by any commitments he may have made. Now though, he appears to barely have a present. Unable even to maintain the most basic rules of conversation, his words are just a scattergun of free association.

Nick Ferrari began Johnson’s LBC radio interview with a few easy rapid-fire yes and no questions as if to establish a benchmark for the lie detector. It proved hard work as Johnson was such a shambles he could barely even confirm his name. Was he a coward? That should have been a no brainer. That’s the one thing on which everyone – even his friends – agree. Johnson merely looked confused. The silence was interpreted as a yes on the polygraph.

Having made some kind of progress, Ferrari moved on to the staged photograph of Johnson and Carrie Symonds in a Sussex garden. Did he know who had taken the picture? “Um... er...,” mumbled Boris. There had been so many photos and so little time. Could he even remember when the photo was taken? A look of panic crossed his face. When you’ve told so many lies, there’s always a danger you might accidentally tell the truth.

Look, said Ferrari, the hair’s all wrong in the photo. It’s much longer than it is now. So this picture was taken months ago. You’ve been taking the public for fools. “Um... er... crikey,” Johnson stammered, trying to rediscover the inner clown tribute act which had proved such a winner in the early years of his political career. The thing about his hair ... The thing about him was he was so virile – literally overflowing with spunk at times – that his hair grew incredibly fast and he sometimes had to have it cut two or three times a day.

There was no more coherence from Johnson when listeners were invited to have their say. Especially on Brexit. The man Tory MPs have staked their careers on is literally clueless about Brexit. His ignorance near total. First, he would get the EU to admit the withdrawal agreement was nonsense. Then he’d set up some badger border patrols in Northern Ireland. As for the £39bn, he’d treat it with some creative ambiguity. Much like his relationships. A need-to-know basis.

But how can we trust you, asked Mike from Littlehampton. You were rubbish as London mayor and rubbish as foreign secretary. “Um... er... wiffle... waffle...,” Johnson bumbled, a bead of sweat appearing on his brow. The thing about trust was that it was over-rated. People had tried voting for politicians they trusted and that hadn’t worked out, so now it was time for someone who could be relied on to let you down and not tell the truth. The kind of unreliability you could trust.

Close to the end, as the interview disintegrated into a gestalt therapy session, Johnson broke down. “People are trying to stop me achieving what I want to achieve,” he sobbed. Finally the mask had dropped and we had the real man. One with the limitless sense of entitlement who believes that normal rules do not apply to him. Being prime minister was only ever a box to tick on his CV. An ego trip of narcissistic self-gratification. It had never occurred to him that being prime minister was about other people’s needs. It had only ever been about him.

Johnson was still a complete wreck an hour later when he gave a second interview to TalkRadio’s Ross Kempsell. Now he didn’t even bother trying to talk in proper sentences. He had regressed so far he was pre-verbal. “Do or die,” he snapped. Brexit as Biggles book. He would do and the rest of us could die. Yes, he might have been slung out by his wife. Yes, the police might have been called to his girlfriend’s flat. Yes, he was basically dossing on the floor, living out of a suitcase with his underpants only held together by the stains. But in his mind he was Mummy’s “King of the World”.

Then came the final implosion. Asked what he liked to do in his spare time, Johnson literally had no idea what to say as even he could see that “shagging” wasn’t an appropriate answer. “Um... er...,” he said. He liked making buses from wooden crates. No, not crates, but cardboard boxes. Then he coloured them in red, wrote £350m down the side, and painted in happy faces of people all saying how much they loved Boris before breaking into a chorus of The Wheels on the Bus Go Round and Round. Call it occupational therapy for a sex and love addict.

Kempsell understandably looked amazed. Even Johnson looked as if he had surprised himself. It was such a pointless, obvious lie. One there had been no need to tell. But he just couldn’t help himself. Lying was what he did. Lying was what he had always done. And it would almost certainly earn him the keys to Downing Street. In the meantime, one of his carers was sent off to make a cardboard bus. Just so they would have something to show the media.