At a time when risque jokes, sexual puns and the habitual chase through suburban bedrooms is pretty tame stuff, bigamy, as a theme for modern farce, is still aberrant enough to keep audiences on the edge of their seats. Will he, won't he get caught? This is indeed the central plot of Ray Cooney's typically British farce, Run For Your Wife, and the fun-filled hanky-panky of London's longest running comedy provided an evening of non-stop laughter throughout last night's opening performance.

The appeal of farce lies largely in the fact that such outrageous things happen to such ordinary people. And Terry Scott, whose comic antics on the stage, TV and films have made him a household name as one of Britain's leading actors, seems to be the epitome of the chap next door -- even if this particular chap leads a highly dangerous double life that lands him in situations that become more and more improbable.

The satisfying, if tiring life of John Smith, a London cabbie who has a wife in Streatham and another round the corner in Wimbledon, is threatened when he gallantly intervenes in a mugging. As he tries, with the reluctant assistance of his upstairs neighbour, to head off the well-meaning but potentially disastrous curiosity of two Policemen, the evening dissolves into a succession of near disasters that keep the audience biting their nails and laughing to the very surprising end.

As the indomitable John Smith, Terry Scott led a brilliant cast that reads like a Who's Who of the London theatre. For those who have never witnessed acting of this calibre it must have been an eye-opener, and for those of us who have, it was a glorious reminder -- if any is needed -- that for sheer technique, British actors are in a class of their own.

Author Ray Cooney, who also directed this production, kept the pace pistol-quick, and such was the professionalism of this cast, that not a line was drowned in the almost continuous salvo of laughter which greeted the equally continuous rain of outrageous puns and innuendos.

The two irate Mrs. Smiths, played by Anita Graham and Judy Buxton (both of whom have performed with the Royal Shakespeare Company) provided marvellous foils for the "harmless old prune'' who nevertheless had snared for himself a gorgeous pair of wives.

Ian Talbot, took on the role of neighbour Stanley Gardner with a display of body language that, in itself, accounted for a large portion of the play's hilarity.

Ron Aldridge and Victor Winding brought a wealth of stage experience to their roles as the Detective Sergeants who, with misguided enthusiasm, attempt to bring order to domestic chaos.

Inevitably, the gay factor had to come in somewhere and in this case it was in the form of a frock-making neighbour (Barrie Gosney), caught up in the general merriment and mayhem.

Apropos of which, one couldn't help wondering if the cast were startled by the guffaw of sustained and ironic laughter that greeted the reference to homosexual practices, as Mr. Smith observed, "It's not illegal any more, is it?'' If they were, let us hope that someone has since acquainted them of the quaint law that still lurks in this Island's law books.

Producer Derek Nimmo, one of the brightest stars in Britain's theatrical firmament, has again presented a play enhanced by a cast who confirm that this form of theatrical entertainment, all too often dismissed by the high-brow, requires acting of very special quality and talent.

And as Mr. Scott remarked, in a charming (and modest) speech to the audience at the close of the evening, "It's nice to start the Festival off with a belly-laugh, isn't it?'' PATRICIA CALNAN FESTIVAL FARCE -- West End stars Anita Graham and Terry Scott in a scene from Ray Cooney's hit, Run For Your Wife, which opened at City Hall last night.