Ateenager pulled from the audience is jammed inside a tiny pop-up tent, while the theme tune to Thomas the Tank Engine blasts out, punctuated by the popping of scores of balloons.

It may sound like the kind of weird dream that comes from a late-night overdose of kids’ DVDs and Stilton. It’s also an insight into the mind of one of Britain’s funniest comedians.

Mark Watson is an odd kind of comic — you won’t find Michael MacIntyre or Jimmy Carr whipping out a Thomas tent at any show soon — and therein lies the appeal.

Despite the silliness, he is not a silly comedian. There’s no self-conscious surrealism or whacky knock-about shenanigans. Neither is there any of that mainstream suburban observational stuff or self-indulgent nostalgia. It’s neither politically correct nor incorrect, because it’s not political at all.

So what is it? Well, nothing really. Watson talks about us, the audience, while making a point not to single any of us out for humiliation (a relief; I find that’s generally the sign of a poor, non-confident and mean-spirited performer). He talks about his drinking, though without seeking sympathy. He talks about getting his hair cut (“Why do they ask if I want it ‘messing up’?” he asks. “I want it doing well!’”). He talks about his life (“I’ve been happily married for four years… out of nine.”), and he laughs about being mistaken in the street (for David Baddiel, of all people).

And, of course, he also talks about Thomas the Tank Engine. Postman Pat too. Venom, if there is any, is reserved for those ubiquitous Keep Calm and Carry On signs.

What we get is affable non-preachy, self-effacing home truths from a slightly awkward Bristolian who sounds Welsh, but isn’t, with a line in comedy which is slightly Jewish in, what he describes as its “neurotic energy” — but also isn’t.

Some comedians like to be introduced by someone saying: “Go crazy for Mark Watson,” he remarks. “But I don’t. I don’t want anyone to go crazy and to do a wee on the stage or anything. And I don’t want to raise expectations.”

He didn’t. And that’s why it was all so funny.