I would be even less surprised to learn that Jacob Rees-Mogg scrapes this muck on to his toast in the mornings. Mogg is the Patum Peperium politician, a unpalatable grey smear that some people claim to enjoy because it represents the class system that validates all their other beliefs. On arrival at Hereford’s Courtyard theatre for an evening of Mogg – a sold-out performance of a new show with the unsettling title Mogg Unbuttoned – I was surprised, then, to see so many people packed in to the lobby and the bar.

But then almost all of them left, filing in to the main theatre to see the comedian Andy Zaltzman. The handful of people who remained resembled the Moggsters I’d expected to see: the very old, and the very odd. Men wearing ties on a Saturday night.

It became clear the reason the event was “sold out” was that it was being held in a studio space with fewer than 120 seats. The woman next to me giggled when I sought reassurance that Mogg Unbuttoned would involve no actual unbuttoning. But what if the nightmare suggested by the title was real?

Mogg is more bivalve than man, an oyster in a double-breasted suit. What if his nanny arrived on stage to ease open the ivory buttons of a shirt inherited from his grandfather? What soft and mottled chicken flesh, what damp, fungus-grey horrors, dangled within?

I steeled myself and wondered if it was possible to scream and vomit at the same time. Mogg was introduced by a short montage of sepia-toned images – Eton, Oxford, parliament, something to do with cricket – and an actor whose job it was to ask pre-agreed softball questions. Above the stage a photo of Mogg as a 12-year-old, wearing his father’s coat and sporting a monocle, was projected on to the backdrop.

This is the character he assumed in childhood: the precocious posho, the son of the editor of the Times, who opened his account with Coutts at 13. Doubtless the young Mogg was told, as confident boys sometimes are, that he was destined for No 10. Perhaps this is why he has spent his life playing the Etonian schoolboy, trying always to remain a person of promise.

His hair is still pasted across his forehead, just as it was back then. His baggy, double-breasted tailoring still makes him look as if he is wearing his father’s suit. He still wears the waistcoat he wore at Eton; he wore it to his wedding, to the state opening of parliament, to the Queen’s funeral.

His toothbrush stands in a mug from the 1977 Silver Jubilee. A more famous image of Mogg – reclining, eyes closed, on the front bench in the Commons – is projected. He says he enjoys the indignation this picture caused, when it was held up as the image of the Tories’ contempt for parliament.

He likes to infuriate the left, he says, with a naughty waggle of the eyebrows. A couple of rows behind me, a man in pink trousers makes a noise like an elephant seal eating a bucket of glue. This is his one joke, which he repeats again and again: top hats, privilege, politics as historical re-enactment.

For nine years after he was first elected as an MP in 2010 he sat on the back benches, a mild embarrassment, until someone found a use for this overcooked cod-Englishness, this weird, low-rent PG Wodehouse act. That person was Boris Johnson, whom he remembers as “wonderful”. He does not seem to understand what his role really was: like Dorries, Grayling, Shapps and Hancock, he was a clown whose function was to make Johnson, the clown prime minister, appear more serious by contrast.

The questions are tossed to him as gently as possible, but then the actor gets one wrong and for a moment the languid veneer really is unbuttoned: Mogg corrects the man icily, a wealthy proprietor angry with one of his staff. For an event sold as leaving “nothing off the table”, this is a controlled performance, full of obviously staged moments and flat, pre-written jokes. There are few laughs, and within half an hour it becomes stultifying.

The conversation turns to cricket and even the actor looks bored. Mogg makes a tedious observation about Rachel Reeves and the pink-trousered man makes his noise again, like he’s bellowing through a throatful of soup. At the interval the Moggites head for the bar, where they form a queue.

That’s libertarians for you: they say they hate to be governed, but give them a taste of actual chaos and they scuttle for an authority to defer to. The paunches are refilled. The Zaltzman crowd emerges, cheeks rosy from chortling; the Moggsters frown at them, frightened and re