Leading article: A Hirst that won't change its spots

"Because it's there" has been the rationale offered by everyone from sea-farers to mountaineers for embarking on an otherwise questionable undertaking. But the challenge thrown out by Damien Hirst – see the simultaneous exhibitions of my spot paintings in all 11 venues around the world and receive a personalised spot print – takes some beating, not least because the average mortal might find it a tad hard to distinguish one set of spots from another. And that is without considering the side issue of whether a Hirst spot painting, where someone else's brush might well have done the painting, qualifies as a real Hirst or should rather be classified as from his atelier. A challenge, though, is a challenge, and two people have already completed it, with another 724 so far registered to take part. Even if he avoided physically painting all the spots, Hirst may find that by the closing date of 18 February, he has quite a lot of personalising to do.