It was 5 years ago today: When Damien Hirst put a sheep in his tank

Five years ago this week, the art world was preparing for the opening of "Some Went Mad, Some Ran Away", a show of works by 15 contemporary artists curated by Damien Hirst, at the Serpentine Gallery in London. Hirst had been nominated for the Turner prize in 1992, but his work - formaldehyde-preserved sharks, dissected cows and calves - had already ensured his wider public profile. The show's potential for reactionary controversy was vast. (Its sculptures included Kiki Smith's Virgin Mary - a flayed, naked woman - and Michael Joaquin Grey's bright orange Balzac, suspended upside-down from the ceiling.)

It opened on 2 May, and reviews were favourable: "High-spirited and stimulating ... this art aims to entertain" (Telegraph); "An eye-wrenching experience" (Times); "One necessarily singular and necessarily eccentric artist's attempts to find or make for himself a like-minded community" (Independent). The FT felt it was "so safe, so predictable, so orthodox".

The Serpentine's centrepiece was Hirst's latest adventure in formaldehyde: Away from the Flock, a disembowelled sheep which had been "rescued" from a knacker's yard. Andrew Graham Dixon thought it was a "kind of self- portrait, banal and sad too: an image of the artist's knowledge that ... he is on his own" (Independent). The piece was sold for pounds 25,000 in the exhibition's first week: "Baa-rmy", said the Sun.

On 8 May, Hirst told the Mail on Sunday that he didn't mind what people thought about his work "so long as they get involved". On 9 May, Mark Bridger, an unemployed artist from Oxford, did just that: he removed the top of Hirst's tank, poured black ink into it and changed the title to "Black Sheep". Bridger gave his calling card to an assistant, who then chased him from the gallery.

"It was very shocking", the Serpentine's director Julia Peyton Jones recalls. "But we dealt with it quickly. We covered the case with paper for the rest of the day so you couldn't see the damage. It was restored overnight [the tank was drained and the sheep's fleece cleaned] and was back on view by 12o'clock the next day. Damien was very upset, but he was extremely pragmatic in dealing with it".

The exhibition became front-page news and, Peyton Jones says, "journalists were aggressive. They wanted immediate access to the piece. The show was already a discussion point; the vandalism compounded it". In the Independent, Brian Appleyard mused that "ink, in the circumstances, might be seen by Damien Hirst as a disappointingly mild response"; in the London Standard, Nigella Lawson asked "if all self-expression is art, what makes this act of vandalism any less the work of an artist?"

That was Bridger's defence at Bow Street Magistrate's Court in August. He said his action was a "positive contribution" to the work; Hirst disagreed. Bridger was found guilty of criminal damage and got a conditional discharge. Despite Hirst's enfant terrible status, Peyton Jones maintains the episode was "a surprise to everybody. I don't want to talk about Bridger's motives. It was a criminal act, it was against the law, it was dealt with as vandalism. It's not the most effective way to make any point about art".