Many years ago, Alan Ayckbourn wrote a very funny play called Standing Room Only set on a gridlocked, London double-decker. But when Sid James was approached as its potential West End star, he declined, telling Ayckbourn: "I'll tell you what's wrong with it. It's a very clean script - it wants a few more rudes in it." Ayckbourn replied: "I thought I'd achieved something monumentally clever by actually avoiding this."

Shaftesbury Avenue has yet to see that show; Ayckbourn's latest, Sugar Daddies, will have no such problems. For a start, it inhabits that febrile alternative world which bears little resemblance to any reality beyond the West End stage. And it has its share of 'rudes'. I never thought to see an Ayckbourn play which relied for its laughs on knob jokes and that rather worn urban myth about the bloke whose mobile is inserted up during a mugging. Time was when Ayckbourn's laughs emerged organically from character and situation.

Still, Sugar Daddies is funny, if well below this writer's best. Sasha rescues a Santa after he's winged by a hit-and-run driver. "You didn't happen to notice if he only had one eye?" he asks. Sure enough, before long said man with the eye patch walks innocently into the play, and the two are revealed as old adversaries. Both claim to be retired Special Branch officers, although it turns out Santa is a semi-retired hood and pimp trying to buy into some purity in his twilight years.

The joy of the show is in three central performances. Alison Pargeter is cast as a country kook just up from Norfolk and very successfully invests the part with native wit and maturity without ever compromising its essential innocence. It's a beaut of a performance and generates loads of laughter.

Terence Booth's one-eyed retired copper is a PC Plod who still clings to the fantasy that his lost eye is a battle wound rather than the spoils of a drunken darts accident. And Rex Garner, the tarnished old geezer trying to regain his virginity through his sassy young saviour, shifts from cuddly lovability to terrifying steeliness and back again, with seamless dexterity - a fine performance from a veteran actor. Anna Brecon as Sasha's half-sister, a metropolitan telly type given to primal yelping, makes her entrance screaming hysterically and then has nowhere to go. And Eliza Hunt's old slag from Val's past has little more to do than justify her presence as a plotting device.

As often happens with Ayckbourn plays in their early days, Sugar Daddies gets over-long in its second half and seems to lose its philosophical way in unnecessary tangents. It will doubtless benefit from some trimming in performance and take its place in his canon as a tidily structured jeu d'esprit.

- Ian Watson (reviewed at Scarborough's Stephen Joseph Theatre)