The new, improved Boris “Mr Serious” Johnson paid a visit yesterday at the Commons press gallery. It’s a dangerous place for a politician at the best of times but Boris likes to think that he’s fearless. I’m sure he wanted to show off his personality transplant. He used to be Boris the Clown. But now he’s running for mayor of London, so he’s had that chip removed (eight hours of surgery) and had one inserted to turn him into Mr Serious.

Why was he there? Who knows. To show us how he’s changed? To talk about bendy buses? To eat? Don’t forget: this was a free lunch. Mr Johnson used to model himself on Bacchus but now purports to lead a sin-free existence in which a sticky risotto may be his only indulgence.

Boris arrived early. This caused a minor panic. He’s always late, sometimes spectacularly so, and once specialised in rushing round like the White Rabbit. Now there he was, standing at the bar clutching a glass of tap water (he’s going to ban bottled in City Hall if he gets in). His eyes looked tired.

I realised, with a sinking heart, that I was going to have to make small talk.

“Do you have an entourage?” I asked politely.

Boris flapped his arms. “Of course! It’s huge!” He pointed to two people who looked in need of a potted plant to hide behind.

People with big personalities are often bad at small talk and Boris is no exception. The transplant has had some effect, though. He’s got a new haircut, so no longer looks quite so much like a haystack that has been attacked by a chainsaw. He was off the booze and his jacket was buttoned up. One result of his becoming serious is that his jokes have become worse. Take, for instance, his new name for Ken Livingstone. “I call him Mayor Leaving Soon,” he noted,“ muttering away: “Yes, I’ve used that one before.”

He then launched, with a resounding belly-flop, into a mayoral campaign speech. It’s always been difficult to imagine Boris running anything more complicated than a bath. So now he peppers his various plans by saying: “We are going to SORT that out,” and “We are going to GET that done!” He sounds a bit like one of those motivational therapists: cheering himself on and on.

He talks of many things but his main obsession is buses. He is close to being Boris the Bus-Spotter. Among his intricate plans for buses is a campaign to stop thugs terrorising the upper deck. “I want a London where adults – yes, adults, that means all of us in this room - are less frightened of kids!”

The moment when he called himself an adult was a bit of a shock. Could Boris really be growing up? Later, during the question and answer session, the man who is no stranger to being exposed in the News of the World was asked a tough question by a female hack: “How are you going to address the fact that a lot of voters, particularly women voters, will worry that a man who lies to his wife will lie to voters?”

This brought an “oooohhhhh”. We waited for his usual bumble and bluster. It didn’t come. “I don’t think that voters really worry about these things in the way perhaps that the media do.” Straight and simple. Not like Boris the Clown at all. Perhaps the personality transplant has taken.

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