Anthony Neilson is a real maverick in the British theatre, a playwright whose brutal, hard-to-watch early plays rode on a mid-1990s shockwave alongside the work of Sarah Kane and Mark Ravenhill. Lately, as an associate artist of the National Theatre of Scotland, he has embraced the large stage and espoused a sort of psychotically based new absurdism.

I missed The Wonderful World of Dissocia at the Edinburgh Festival in 2004, but much enjoyed last year’s companion piece, Realism, a modern Oblomov in which the repellent sleazebag of an anti-hero lives the kind of extraordinary day he would have done had his own real life not been so boring.

In Dissocia – brilliantly revived for a national tour with the Drum Theatre, Plymouth, and the Tron, Glasgow – Neilson dramatises the mental state of 36-year-old Lisa (Christine Entwisle), a dissociative identity disorder patient – in stark metaphorical bipolar fashion. The first act is like Alice in Wonderland with sex and violence, the second like Beckett without the jokes, bleached to antiseptic white neutrality.

Without medication, in the first act, Lisa travels like Lewis Carroll’s Alice to the topsy-turvy world of Dissocia after a zany Swiss watch fixer (Barnaby Power) advises her to go in search of the hour she lost on a flight back from New York and restore balance in her life. She takes a lift to Dissocia, encounters some bottom-scratching insecurity guards (Jack James and Matthew Pidgeon), a posse of oatcake-eating oath-takers, and a bizarre, blowzy lost property manager (Claire Little) serving hot dogs to customers who have lost much more than an hour: a sense of humour, an argument, their inhibitions. There’s always someone worse off than yourself.

The land is haunted by the menace of Black Dog (that telltale symbol of depression), and the natives intone an anthem to Dissocia, where they’ll “even make a boat for ya” (not as good a lyric, perhaps, as the executioner’s song in the Land of Ambrosia “where everyone knows ya”). Lisa is about to be raped by a randy goat (James Cunningham) when a bloody, battered council worker (Amanda Hadingue) turns up with a clipboard to assume a replacement role of abused victim and take her on a Chitty Chitty Bang Bang-style flying buggy ride over the stricken land to bomb the enemy.

On press night, I could sense sophisticated metropolitan Royal Courtiers, and one or two toffee-nosed critics, seizing up in horror at all this, but I relished the refreshing theatrical silliness of it all, the admirable dedication of Neilson’s eight-strong company (the playwright directs his own plays, indeed he writes them in rehearsal with the actors) and the grim black humour of both the civic satire and the extremity of Lisa’s “dream”.

The short second act is an ironic series of blank tableaux with Lisa sealed off behind a Perspex hospital ward in her bed, attended by medical staff and finally her boyfriend who cannot understand her, cannot abandon her. She finds a smaller pet version of the polar bear who sings for her in Dissocia and a ray of coloured light seeps onto the stage. She will return…. It is the bleakest conclusion to the funniest play seen in Sloane Square for a very long time.

- Michael Coveney