<preform>Mercury Fur, Menier Chocolate Factory, London</br>Breathing Corpses, Royal Court, London</br>Insignificance, Lyceum, Sheffield</preform>

Battling through the rain and dark, past deserted goods yards and railway arches, it didn't feel that safe on the streets of Southwark. And I certainly didn't stagger away after Philip Ridley's apocalyptic new play, Mercury Fur, feeling any cheerier about inner-city London. His vision of drug-addled youths and shocking crimes is so polemical that it caused a rumpus before it even opened. Allegedly, Faber refused point-blank to print it.

Battling through the rain and dark, past deserted goods yards and railway arches, it didn't feel that safe on the streets of Southwark. And I certainly didn't stagger away after Philip Ridley's apocalyptic new play, Mercury Fur, feeling any cheerier about inner-city London. His vision of drug-addled youths and shocking crimes is so polemical that it caused a rumpus before it even opened. Allegedly, Faber refused point-blank to print it.

The Menier is a terrific venue and John Tiffany's production for Paines Plough is grippingly visceral, but be prepared to feel winded. The audience is cleverly rendered vulnerable at the outset. Groping towards a distant torch beam, you pass through a wrecked child's bedroom into the main space: a sea of litter, broken toys and upturned armchairs. This is, we gather, an abandoned east-end council block in the not-so-distant future. Two skinheads, Ben Whishaw's scrawny Elliot and his brother, Robert Boulter's Darren, break in with a crowbar and start hastily preparing for a "party". To call them foul-mouthed would be putting it mildly, and Elliot, when irked, shouts a nonsensical torrent of multi-ethnic abuse ("Chinky, Muslim, Christian cunt", etc). They are interrupted by Naz (Shane Zaza), a squatter who, like Darren, is addicted to hallucinogens called butterflies which generate lurid fantasies about, say, rape or political assassinations. Elliot, who deals but doesn't touch the butterflies, has some grasp of the past. The others' brains appear to have been scrambled, and this may relate to a mysterious shower of "sand" that has fallen over the metropolis. Neither Naz nor Darren seem too bothered about the unconscious child whom Elliot lugs in as the so-called party piece for their guest. The latter is a rich guy with government connections who wants to star as a paedophile in a snuff movie. By the end, everybody is blood-splattered and screaming as a bombing-raid shakes the city.

One might complain that Ridley is a puerile shock jock. There are some clunking revelations and predictable juxtaposing of the brutal and the sentimental. One might also wonder if the playwright isn't indulging in his own nasty fantasies or even encouraging copycat sadism. In many ways, Mercury Fur is the new Clockwork Orange. Nevertheless, in the current climate of increasing censorship by simplistic fundamentalists (cf Behzti, Jerry Springer, etc), Paines Plough and Methuen are doing the right thing. Publish and be damned.

Moreover, Ridley is writing in the tradition of Greek and Jacobean tragedies. He underlines that brutality warps, suggests that love and morals persist, and is deliberately creating a nightmare scenario rife with allusions to actual world news. Tiffany's traverse staging increases the discomforting intimacy.

Dominic Hall is tediously bullish as the party guest, but Whishaw (formerly Trevor Nunn's Hamlet) exudes terrific febrile intensity, and Fraser Ayres as the sinewy gangland chief, Spinx, is transfixing too. This show should, at the very least, provoke interesting ethical rows.

In Laura Wade's new play, Breathing Corpses, one mangled woman's body is rotting in a storage crate and another has been dumped in a city park. Wade's recent premiere, Colder Than Here, was about a terminally ill mother attaining serenity; Breathing Corpses is more darkly twisted. We start in a hotel room where a chambermaid, Amy, discovers that the bed's occupant is dead. Next we cut to a storage depot where the affable boss, Jim, wanders off to check out said storage crate. Cut to Kate and Ben, a viciously unhappy couple.

Having played games with time, Wade comes full circle, back to Amy re-entering that hotel room. Unfortunately, the wheel also turns 360 degrees in terms of dramatic weaknesses and strengths. Amy's first soliloquy rings very false and the next two scenes feature verbose monologues.

That said, Kate and Ben's (Tamzin Outhwaite and James McAvoy) sadomasochistic relationship packs a disturbing punch. After Paul Copley's Jim is traumatised by opening the crate, the disintegration of his marriage to Elaine (Niamh Cusack) is sensitively portrayed. However, not all Anna Mackmin's cast are fine-tuned and the implied daisy-chain of events doesn't actually make temporal sense - unless Amy is a ghost or some kink has developed in our space-time.

Terry Johnson's comedy of ideas, Insignificance, deliberately plays with such possibilities, as Einstein, Marilyn Monroe, Joe DiMaggio and Joseph McCarthy all materialise in the same hotel room, with the Senator claiming the other three are just in his head. This modern classic from 1982 memorably blends intellectual stimulation and entertainment, as the Actress tells the Professor she knows all about the theory of relativity and proves it with toy trains.

However, what comes across most strikingly in Sam West's revival is a sense of reinvigorated topicality. It's not just that our society seems more obsessed with celebrities than ever before. There is also something horribly familiar about Gerard Horan's swaggering Senator, threatening the civil liberties of anyone he suspects of un-American activities. Mary Stockley does a lovely breathy impersonation of Monroe, and Nicholas Le Prevost's Einstein is adorably scruffy, dignified and privately wracked about his part in the development of WMD. Indeed, apart from a distractingly reflective silvered set, there's little to fault in this touring production. It certainly bodes well for Sheffield's twinned theatres, the Lyceum and the Crucible, where West will be taking over the reins from Michael Grandage in June.

k.bassett@independent.co.uk

'Mercury Fur': Menier, London SE1 (020 7907 7060), to 27 March; 'Breathing Corpses': Royal Court Upstairs, London SW1 (020 7565 5000), to 19 March; 'Insignificance': Lyceum, Sheffield (0114 249 6000), to Sat, then touring