The power of the internet to sell art was proved last year by the petcat of "Young British Artist" Tracey Emin (pictured). When she lost her cat, Emin made a reward notice, photocopied it and then plastered the poster around her east London neighbourhood. As soon as people realised that Emin had made the posters, they took them home and offered them on eBay, the online trading company, for £500.

This power has been clear for some time, however, on more impressive levels: namely, that price or rarity are no barrier. In June 2000, a copy of the first printing of the American Declaration of Independence, of which 25 are known to exist, sold on the website of the auctioneers Sotheby's for $8.14m, and a double portrait by Frederic Lord Leighton sold there in 2001 for half a million dollars. Nor is this only for ignorant spendthrifts; even museums have bought online.