The Island of Slaves, Lyric Hammersmith <br></br>Vincent in Brixton, NT Cottesloe, London <br></br>Edward III, Swan Theatre, Stratford-upon-Avon

The cockney, the clown and the curlicues

How wonderful. We've all been raised up on high. On wandering into the Lyric Hammersmith's Victorian auditorium, you discover the old place has undergone a radical upheaval for Neil Bartlett's fine production of Marivaux's forgotten gem, The Island of Slaves. The stalls have disappeared and the audience sits on the stage which has been extended out to meet the dress circle. The floor is covered with sand and, as the sound of ocean waves surrounds you, the theatre's stucco curlicues start to look like foaming breakers.

That's apt for this comedy in which Harlequin and his la-di-da master, Iphicrates, roll up as shipwrecked castaways. It's symbolically fitting too since this piece – first performed in Paris in 1725 – is also a startling, political problem play that centres around the issue of being socially "upgraded". Marivaux's isle is Harlequin's topsy-turvy Utopia. Founded by rebel slaves, it's an alternative state where he and Cleanthis – maid to Euphrosine – are hailed as "comrades" by the local, Trivelin, and given sway over their hitherto bullying master and mistress.

The classes swapping clothes is, of course, a classic formula for fun. And though this sophisticated version of commedia dell'arte is above acrobatics, Guy Dartnell's Harlequin clowns round a bit, wriggling out of his trousers like a strip-teaser. High romance is sent up too when Dartnell and Anita Dobson's wiry, cockney Cleanthis start swanning around, attempting to seduce each other in "pukka" accents.

Actually, Marivaux is more often unsettling than entertaining as nasty realities creep into his dreamy worlds. His plays feel like lab experiments too, where human beings – under surveillance – often appear cruel and morally skewed. The island of slaves definitely isn't a wholly wonderful, brave new world. The posh are put on trial, and the witnesses prosecuting them want vengeance rather than justice. Further questions hang over Trivelin's judicial creed as he advocates punitive humiliations to "re-educate" offenders.

Bartlett's cast, in evening dress, apparently inhabit the mid-20th century but it's the timeless pertinence of this play that's striking (especially as his translation is plain-spoken rather than in period lingo).

Not only did Marivaux anticipate the French Revolution and Marx: his protagonists make one anxiously muse on reconciliation processes in post-apartheid South Africa and our own class-divided society and penal system.

Bartlett's cast are a strong ensemble. Dartnell feebly milks the odd joke, but his sarcasm has yobbish menace. Dobson is like Eliza Dolittle crossed with a snarling, wounded Jack Russell and Amanda Harris's Euphrosine manages to convey terror underneath her incurable superciliousness.

Bartlett's previous production of Marivaux's The Dispute was more searing, but he ensures The Island of Slaves is both witty and worrying. The "happy ending" is particularly ambivalent, for when Dartnell finally hugs Gregor Truter's sobbing Iphicrates, that forgiving gesture seems at once touching and, maybe, foolish. Obviously it's a loaded word, but this is enthralling.

Class tensions also crop up in Vincent in Brixton. Nicholas Wright's new play about Van Gogh focuses on the Dutchman's early years in London when he lodged in SW2 and worked as a junior art dealer (his uncles' middle-class trade). Picking up on faint allusions in Van Gogh's letters to some passionate attachment, Wright pictures Vincent losing his innocence in a household where extra-marital love blossoms, at odds with his puritanical upbringing. After having his aesthetic opinions challenged by his working-class fellow-lodger, who scorns highfalutin art, Vincent embarks on a formative love affair with his landlady, Mrs Ursula Loyer. Eventually coming back to her after some years, almost destitute, he begins to develop his raw talent as a painter.

Richard Eyre is on top form staging this Cottesloe production which also marks his first return to the National since Trevor Nunn took the helm. What is engrossing here is that Wright's poetic licence is combined with acutely observed domestic realism. Tim Hatley's set, on a traverse stage, is a beautifully detailed tranche of Victorian life complete with kitchen sink, earthenware pots, and an iron stove on which Clare Higgins's Ursula rustles up supper.

It must be said, the final act drags a little, with Vincent's zealous Bible-quoting side coming to the fore. A few key speeches also border on the sentimental. But elsewhere the quiet, psychologically precise charting of complex, shifting relationships is very fine, with lovely flashes of comedy and sharp slides into despair. Jochum Ten Haaf's shy but impulsive Vincent can be a hilariously awkward innocent, and Higgins is superb, with a matronly front, heart-rending tenderness and bitter fits of depression. Also, for fast-rising talent, watch out for Emily Blunt who plays Ursula's brittle daughter, Anna.

The RSC is promoting young directors in their new Swan season of rarely aired Jacobean dramas. Unfortunately, Edward III, which is being boldly attributed to Shakespeare, isn't as exciting as one might have hoped. Edward Hall – regarded by some as a potential heir to Adrian Noble – stormed out, reportedly complaining about insufficient rehearsal time. So Anthony Clark, who's more of a summer than a spring chicken, stepped into the breach.

He's done a generally impressive job. This is a well-drilled, pacy production, though the mix of modern props (Biros) with medieval gear (chain mail) is bizarre. There's also an intriguing romance at the heart of this chronicle where David Rintoul's King Edward tries to ignobly seduce Caroline Faber's Countess of Salisbury. Faber is fascinating: teasing, clever, passionately moral. On the issue of authorship, her ethical arguments seem persuasively like a prelude to Measure for Measure. But sometimes this play sounds like the Bard with a labouring apprentice in tow, churning out imagery mechanically. Rintoul is rather stolid and his wars with France bang on forever. Academically interesting but a hard slog.

'The Island of Slaves': Lyric Hammersmith, London W6 (020 8741 2311), to 8 June; 'Vincent in Brixton': National Theatre Cottesloe, London SE1 (020 7452 3000), booking to 15 June; 'Edward III': Swan, Stratford-upon-Avon (0870 609 1110), to 14 September

k.bassett@independent.co.uk