The School For Scandal, Park Theatre

What to do with an old warhorse like The School for Scandal, a fantastic play written by Richard Brinsley Sheridan in 1777 full of smart lines and great parts, beloved not just of professional actors but amateur troupes too - and therefore performed with sometimes monotonous regularity? Well, if you're director Jessica Swale you cut a bit, add a bit and give it some musical numbers while remaining mostly faithful to the original.

It's an approach that she used on another of Sheridan's comic masterpieces, The Rivals. Here, the actors, in period garb but making some pointed modern references, introduce the action by way of a musical prologue (the first of a few such interludes), written by Swale and Laura Forrest Hay, warning us of the dangers of tittle-tattle. Tittle-tattle, idle gossip and just plain old lying are pretty much all that this play's characters indulge in, but in beautifully barbed language.

The action begins in Lady Sneerwell's drawing room, where today's character assassination is of Sir Peter Teazle – no fool like an old fool – who has taken a much younger bride (Daniel Gosling and Kirsty Besterman, sparring nicely off each other), and the rakish Surface brothers, Joseph (a suitably snake-like Tom Berish, pictured right with Besterman) and Charles (Harry Kerr), whose rich uncle, Sir Oliver (Timothy Speyer) is soon to return to London from the Indies.

An array of characters, each more fatuous than the last, come to parade their spite, while maintaining a hypocritical innocence of their deeds. As Mrs Candour says while passing on some juicy titbits: “Tale-bearers are just as bad as tale-makers.” Sheridan's play - about greed, deception and artificiality - hammers home the point that human beings can be a pretty nasty bunch. Even the “nice” characters - Sir Peter and Sir Oliver - are bumptious idiots. But this is a morality play, so the baddies eventually get their comeuppance after much masquerade, double-dealing and backstabbing.

Belinda Lang is superb as Lady Sneerwell, controlling those around her like chess pieces on a board, and Buffy Davis does a suitably over-the-top turn as Mrs Candour, while Jessica Clark plays Sir Peter's ward Maria - so often a role that goes unnoticed - as a cross between a huffy teenager and a haughty young heiress.

There's some great ensemble acting, but Sheridan's razor-sharp humour is often blunted by overly broad delivery and one or two roles are miscast. And, even though the auditorium runways and balconies in this compact theatre are used throughout and Simon Kenny's simple design gives the cast the full stage to work on, much of the staging feels cramped and static. That said, there's fun to be had.

• The School for Scandal at Park Theatre, London N4 until 7 July