It’s odd how sometimes you can have a tasty collection of ingredients but when you put them together the result can be half-baked. The Mentalists is a comedy by Richard Bean, creator of such memorable productions like One Man Two Guvnors, The Big Fellah and Great Britain. He also wrote the book for the excellent musical Made in Dagenham. He also wrote Pitcairn, but we can gloss over that. In the role of Ted we have Stephen Merchant, a naturally funny man who can create laughs out of thin air, and whose gangly appearance and self-deprecating humour are a gift for any chat show or stand up routine. It also features Steffan Rhodri, as Morrie, best known as Dave Coaches off Gavin and Stacey, who proves himself to be an assured comedic actor on stage.

I had assumed this was a new play by Mr Bean but in fact it is a revival, the original production having been staged at the National in 2002. That explains why you feel that, although the play is set in the present day, there are some slightly outdated aspects to it. The setting is a seedy hotel room in Finsbury Park, even though Ted wants the outside world to think he’s in Exeter. Richard Kent’s set is delightfully underspecced, consisting of grimy wallpaper and a dismally small TV, and with those hideous floppy brown sliding doors around the ensuite giving the perfect finishing touch to what would be a most disappointing place to spend a night.

Messrs Merchant and Rhodri chuck as much life at this play as they possibly can, with excellent comic timing, flawless vocal delivery and a nice sense of the ridiculous. But, oh, the play. It starts promisingly, with the pair turning up at this gloomy hotel, one of them on a mission to do something (what, we don’t know), the other there to help out. We get an amusing insight into Morrie’s life, a serial womaniser and fantasist, making a living by ducking and diving, ostensibly a hairdresser by trade, but primarily by making soft porn videos. Ted, which I presume is short for Tedious, remains something of an enigma, even long into the first act where he is filmed spouting some self-help home-spun philosophy about how to create an Utopia (for £29.99).

At some point during a very dull scene where Ted is churning out this philosophy, I faded out. Then came the interval, with people around me muttering to their companions, “do you understand what’s going on?” I was relieved to hear that they were as confused as I was. The second half isn’t much better, but the story is resolved to the extent that you discover Ted is much more troubled than he appeared to be, and he’s probably going to have a really rotten time after the play is over. There’s a bizarre scene where Morrie, in hairdressing mode, decides to give Ted a shampoo and head massage. At the same time the police are trying to break into the hotel room. Does it sound funny? It isn’t really.

The character of Ted is a right-wing, Mail-reading xenophobe and I found a lot of the “jokes” mildly offensive. The play also takes the subject of mental illness and deals with it in an easy, facile, rather disrespectful manner. Structurally the play is quite weak, with the closing lines of both acts ending on a whimper rather than a bang, so that no one knew whether to applaud or not; and I’m not really surprised it’s closing early. Great performances can’t save a boring text, I’m afraid.