Can you believe it’s 25 years since Trigger Happy TV – which made Dom Joly a household name – first started broadcasting, since when he’s had several TV shows, written many books, and done a couple of live tours. The Conspiracy Tour marks his return to the stage after many years absence and – as he admits himself – is basically a book tour, publicising his new opus The Conspiracy Tourist, where he meets conspiracy theorists around the world from the bizarre to the bonkers, and even the occasionally perfectly sane.

He cuts a commanding figure on stage; relaxed, confident and thoroughly at ease. He maintains he doesn’t tell jokes – probably true – but that doesn’t stop the evening (or the first half at least) from having plenty to laugh at. He presents us with an inverse pyramid of theories; at the upside down apex, ideas which are within a hair’s breadth of reality. At the other end of the scale, stuff that’s completely doolally. And he takes us through a few of these ideas to test their reasonableness, and then raconteur his way through his experiences, trying to prove or disprove them.

For example, did you know that some people think that Finland doesn’t exist? That it’s an invention between the Russians and the Japanese to fish the waters of the Baltic and then secretly transport their catch eastwards? They believe that anyone who says they are a Finn is really a Swede. Hmmm. Well, I’ve been to Finland three times and can attest there is definitely land there. And would they really doubt the word of the great Lasse Viren? That one’s bonkers.

But what about Denver International Airport? No one doubts that its existence, but what secrets might it be hiding? Do you believe in UFOs? Dom Joly’s been to Roswell to find out (so that we don’t have to). And how about the assassination of JFK? At the top of the scale is where the Illuminati sit side-by-side with the Flat-Earthers, and Mr J has even been to Fogo Island, Newfoundland, where that latter group believe one of the four literal corners of the earth is situated (Clue: it isn’t.) There’s no doubt that he’s put the work in to make his book a definitive account of conspiracy theories and, as a comedy lecture, the first half works well.

However, after the interval things fall apart somewhat. After a lengthy introductory video, we meet Dr Julian Northcote, conspiracy theorist extraordinaire, who regales us with a few stories and attempts to prove his ridiculous ideas. Spoiler: it’s Dom Joly in a wig and glasses doing what feels like an impersonation of a Harry Enfield character. Once he’s been bundled off stage for improper behaviour, Mr Joly returns for a Q&A session; this always strikes me as being a way of a performer saying I can’t quite work out how to end this show, so you end it for me. There were a few questions about conspiracy theories, about which Mr J was rather dismissive, I thought; and a few questions about the Trigger Happy days with which he was more comfortable. It ended with a final look at conspiracy theories and the promise of an assignation in the foyer to buy his book and take selfies. And, to be fair, he had quite a queue forming when we left.

A curate’s egg of an evening, but when Mr Joly gets going on the subject of his expeditions to sort the wheat from the conspiracy chaff, he’s on great form. Only a couple more shows left of his tour now – in Carlisle and Stockton-on-Tees.