This has two unfortunate results: the more problematic plays (Timon, All's Well, even Othello) have become marginal. Andwith so many precedents lined up, directors of the popular plays have to scrabble around for something new to say. If a production doesn't feel fresh, it isn't going to work; and when the plays are coming round every three or four years, freshness becomes a valuable commodity.
Even if the director has new ideas, there are strict limits on how he can express them - the RST in Stratford and the Barbican in London are both big theatres. Filling them isn't easy, either in the sense of bums on seats or of creating a spectacle on the necessary scale. So, nothing too small, nothing too radical. They're neither of them very congenial spaces, either - any actor who has to try and get laughs at the RST especially has my sympathy. A couple of weeks ago, at Adrian Noble's unhappy Twelfth Night (the sixth production there in the last 20 years) you felt you could almost see the jokes plummeting down, thud, somewhere around the third row of the stalls.
Plans are afoot to raise funds for the remodelling of the RST's interior. But that's tinkering. What the RSC really needs to do is rethink its policies: to vary the repertoire on its main stages - less-seen Shakespeares and a few more non-Shakespearian plays - and to move the big crowd-pleasers to the smaller stages for a change.
In the meantime, we have to put up with things like Noble's Twelfth Night and Gregory Doran's The Merchant of Venice (the sixth production at Stratford since 1978). Not that this is a positively bad staging. There are many incidental pleasures - such as Jimmy Chisholm's prancing globule of a Launcelot Gobbo - and thoughtful if uneven performances by Helen Schlesinger as Portia and Julian Curry as a puritanical Antonio. I have to admit to being disappointed by Philip Voss's Shylock. Partly that's because I'm an admirer of Voss and was hoping for something remarkable. Indeed, in the opening scenes he drops hints that he really is going to be remarkable - oily and villainous, he's a worryingly alien, predatory creature, so that when Antonio pulls away from a handshake in disgust, you can see his point. But as the grieving, aggrieved father, Voss is a little too controlled.
Doran evidently has some ideas about the play, too. For one thing, he's clear that anti- semitism is deeply rooted in this society - so Robert Jones's oversized, plasticky set places Shylock in a dank, louring ghetto (a Venetian invention, after all), through which gentile revellers career in pig's-head masks. But the ideas aren't followed through. You never feel that Doran has something he really wants to say.
The general awfulness of the RST has to be contrasted with the buzzing intensity of productions at the Swan. Laurence Boswell's production of Ben Jonson's Bartholomew Fair doesn't always maintain a high pitch of energy (though there are times when you wish it would just slow up for a moment so you can catch your breath).
Jonson's sprawling panorama of London types at play has been translated here to a Notting Hill-style carnival inhabited, in Tom Piper's gaudy design, by a gallery of contemporary types: the hard-drinking, argumentative John Quarlous (Rob Edwards) is a Withnail-style bohemian in a long leather coat; the singer Nightingale (Jon Clairmonte) is a cool West Indian guy with an electric guitar; Mooncalf (Steve Swinscoe), who helps out at Ursla the pig-woman's booth, is a nerdy, solvent-damaged punk.
The parallels are logical, and the directness and astonishingly undated tone of Jonson's comedy means that it can handle a good deal of modernising. Shakespeare's joke rarely survive as well in performance as Jonson's. Many of the performances - Stephen Boxer's fussy, eccentric Littlewit, Poppy Miller as his lovely young wife - are perfectly pitched, and individual sequences work brilliantly. Master Cokes's dance, daring the local cutpurses to pick his pocket and getting well and truly fleeced as a result, is a masterly bit of sustained buffoonery by Tom Goodman-Hill.
Over three and a half hours, however, the play (and the audience) starts to feel the strain. The production is too insistently modern; Boswell could afford to acknowledge that Bartholomew Fair is 400 years old, and to let some of the jokes and characters exist on their own terms, rather than shoehorning them into 20th-century types. It's all a matter of swings and roundabouts, really. By the way, like The Merchant of Venice, this production uses artificial pig's heads, which is frustrating: if I'd known in advance, I could have made a killing on the artificial pig's head market.
Wholehearted praise, finally, for More Grimm Tales at the Young Vic. Carol Ann Duffy's versions of the original German folk-tales (rather than the tamer versions we know) are pleasingly unmodernised and unbowdlerised. The hare who is stupid enough to race the hedgehog finally dies from exhaustion, with a pretty red ribbon of blood trickling from his nostril. Animals' eyes are gouged out and chucked round the stage.
As with his production of The Jungle Book a couple of years back, Tim Supple manages the trick of making the narrative accessible and exciting for children without losing any emotional punch or intellectual bite - the wolf who attacks Little Red-Cap has just the right edge of sexual aggression, without actually swallowing Angela Carter whole. Supple has an excellent ensemble cast - Linda Kerr Scott, in particular, manages to give a brilliant impression of one of the stalky, nubbled grotesques in Mervyn Peake's illustrations to the stories; while Andy William, in grey long-johns and mottled donkey- jacket, is a startlingly realistic wolf. I went to a matinee full of children of primary school age, and they lapped it up. Your correspondent, meanwhile, was turning green and groping for a paper bag. Kids, eh?
'Merchant of Venice': Stratford RST (01789 295623), in rep to Aug; 'Bartholomew Fair': Stratford Swan (01789 295623), in rep to Aug; 'More Grimm Tales': Young Vic, SE1 (0171 928 6363), to 31 Jan .
Robert Butler returns next week.