XXX, Riverside Studios, London, ***

The woman sitting next to me felt like throwing up when it was finally all over. The video clip of a real vagina being sewn up as it seeped blood, projected on to a vast screen on the stage, certainly didn't help. Such was the punishment meted out to the mother of 18-year-old Eugénie in XXX, a drama based on the Marquis de Sade's book Philosophy in the Bedroom by the Catalan troupe La Fura dels Baus. It tells of the sexual indoctrination of Eugénie by two men and a woman. The girl then turns her newfound skills on her mother as revenge for her moralistic upbringing. Before the gruesome needlepoint, Eugénie rapes her with a strap-on.

The relentless fornication was achieved with prosthetics twanging through trouser flies (anyone concerned that they were witnessing the real thing need only compare sizes when the actors eventually took off their underpants). Also faked was the volunteer from the audience (the Spanish accent was one give-away) who allowed Eugénie to perform oral sex on the flaccid faux phallus dug out from his boxer shorts, as were the supposed live camcorder shots of the audience playing with each other after pheromones were allegedly pumped into the auditorium.

What was genuine (the actresses' cellulite-clad bottoms also had the ring of authenticity) were the video clips, which included a woman with a penchant for ponies; orgies; a defecation close-up complete with splat on the camera lens; a nipple being surgically cut into; and a prolonged cum-shot. Not bad for 25 quid.

The show swings between the disturbing and the boring, the revolting and the ridiculous – sex while writhing in spag bol was a particular humdinger. Just as one became numbed by the marathon of copulation, a dash of deviance was thrown in to send one's eyebrows soaring back northward.

To its credit, the troupe remembered that sex is not without humour. Pau Gomez as Giovanni raised a laugh with his eye-to-eye conversation with his penis, as did Teresa Vallejo, as the Madame, when boasting that the sex toy modelled on her genitals ("the deluxe version has an arsehole") had sold more copies in America than the Bible. Pedro Gutierrez was so convincing as a sexual predator that one would happily have taken a mallet to his ubiquitous penis had one not suspected that he would rather enjoy it.

Quite what is the point of it all, if any, is still in question. Will it make us less prudish about sex? Of course not. Certainly, we all sat through the production with our legs open, but that was because the seats were packed so tightly together that one couldn't close one's knees.

To 17 May (020-8237 1111)