“This is going on longer than a European fisheries meeting,” grumbled Boris Johnson as the Treasury select committee drifted well into its third hour.

“That’s because you keep making lengthy interruptions,” the committee chairman, Andrew Tyrie, observed.

This only provoked yet another crowd-pleasing interruption. Boris just couldn’t help himself. His grasp of detail is minimal, his attention span shorter than the average five-year-old’s and when boredom sets in his default setting is to carry on talking until he gets round to saying something that amuses him. All of which may explain why he is a charismatic, populist politician but is less than an ideal when a little gravitas is required. To treat a select committee as the fall guy in your own personal TV gameshow is the ultimate in lese-majesty; especially when you are auditioning for David Cameron’s job.

“I talk to loads of bankers,” Boris had said at the start of the hearing, “and I can tell you their support for the EU is a great deal more shallow than commonly believed.”

“What you’re hearing in anecdotal meetings seems at odds with the evidence I’m hearing,” Tyrie replied. “Can we go back to the speech you made in Dartford on 11 March? Have you checked the methodology of the statistics you quoted?”

No chance. Boris can barely remember what he said the day before, let alone some numbers he may have trotted out a couple of weeks ago. Besides what he really wanted to talk about was European bureaucracy gone mad. Legislation that prevented children under the age of eight from blowing up balloons; directives that meant councils were unable to recycle teabags; one-size-fits-all Euro coffins (how were we meant to squeeze our fatties into them?); French lorry manufacturers deliberately setting out to murder cyclists.

On and on he went despite several pleas from Tyrie begging him to stop. Eventually Boris paused for breath and Tyrie managed to make himself heard. “This is all very interesting, Boris,” he said. “Except none of it is really true, is it?” Boris looked put out. So what if it wasn’t exactly true? It got a few laughs so it ought to have been true even it it wasn’t. “If I may say so you’re guilty of exaggerating to the point of misrepresentation.”

Boris looked mildly hurt by this. “Well,” he went on, “I’ve got this new piece of research hot off the press, published today by the House of Commons library saying that 59% of British legislation is imposed by the EU.”

“Actually that was published in 2014,” Tyrie pointed out, “and the figures were between 15% and 59%, depending on whether individual decisions were put into the calculations.”

Time for some top banter. “Well I’ve just found this piece written by one Andrew Tyrie in 1991 which says the single market can only be complete with a single currency,” said Boris, “What do you say to that?”

“Oh dear,” replied Tyrie a touch acidly. “That merely proves my point. If you had read the entire article you would have realised I was saying the exact opposite.”

Labour’s Helen Goodman and Wes Streeting tried to pin Boris down on whether he thought Britain should be negotiating a Swiss or Canadian trade deal with the EU post-Brexit. “One day you say one thing, the next day you say another,” they said. “You seem to change your mind a lot.”

“Not at all,” fought back Boris. “I’m entirely consistent.” As in entirely consistent in his inconsistency. “What I want is a British trade deal. It will be a complete doddle. EU countries will be falling over themselves to do a deal with themselves.”

“You’re the only person who seems to think that.”

“Everyone else is far too defeatist. As I’ve always said. Britain will be massively better off outside the EU,” said the man who had apparently been anguishing which camp to join over a game of tennis the day before he joined the leave campaign.

Enter an even angrier than usual John Mann, who had woken that morning furious to find he had been listed only as “core negative” on the leaked Corbyn list of Labour MPs. Why not a hostile? He was hostile enough to his own reflection, let alone others in his party.

“This so-called EU animal byproducts tea bag directive,” he snarled. “Can you remember which country asked the EU to issue it?” Could pigs fly? “Well let me tell you that it was Britain after the foot and mouth epidemic.”

“Then I’m sure the French have never obeyed it,” Boris ad-libbed, desperately searching for one last laugh. None came. Boris was beaten, if unbowed.