The Mentalists (Wyndham's Theatre)

Richard Bean's third major play was part of the National Theatre's "Loft" (temporary theatre) season in 2002, and it proves well worth another look in Abbey Wright's perfectly pitched production starring the improbably tall Stephen Merchant, wide-eyed and appropriately peculiar for a cranky ideas merchant, and short, blustery Steffan Rhoddri as his sidekick with a video camera.

Merchant's Ted, fleet manager with a car firm in Swindon, and Rhoddri's Morrie, a north London unisex barber, have checked into a bed and breakfast "hotel" in Finsbury Park to make a film, or an advert, or a party political broadcast of some kind.

They are an odd couple, alright, working class lads who've done fairly well, having bonded as Barnado's boys, and they share a belief that the world is going to hell in a handcart. What do they teach kids at school these days? They don't even know who Oswald Mosley is. For some reason, Ted blames woodwork teachers for the indolence of youth.

Ted's wonky homilies, inspired by the barmy utopian visionary and psychologist, B F Skinner, are punctuated with the more earthbound, equally hilarious Pinteresque riffs of Morrie, who laments the lack of a decent sandwich on offer down the Seven Sisters Road since Bill Gates – "who used to sell sarnies off the back of a push bike" – discovered the internet and the money to be made from selling shots of cocks to Japan.

Bean is making merry here with his experience as both a stand-up comedian and a sit-down psychologist. What's particularly impressive is his ability to suspend a joke or tall tale's pay-off, or end it in an unexpected way, or bring back the up-front story of the perfect murder into play towards the end.

There's an interest, too, in the character-forming fuel of both oddness and fanaticism, a theme that runs through his remarkably varied and often exceptional plays of the past ten years. I now find myself impatiently awaiting the next new Bean feast, and I think the revivals of his early work – Toast at the Park, and now this play – only serve to underline his pre-eminence in our theatre.

In some ways, Merchant and Rhoddri reverse the physicality of the original actors, Michael Feast and Duncan Preston, but they certainly reiterate the characters' respective contrast in nuttiness and knottiness. Merchant doesn't "come on" to the audience too much, all the more disturbing for being placid behind that looming moon face and those circular specs. And Rhoddri's normalcy and affability make him a more than plausible pornographer. A lovely show.

The Mentalists runs until 26 September. Click here for more information and to book tickets.