Hugh Grant, the actor, pocketed a profit of more than £9m ($17.9m) when he sold a silkscreen print of Elizabeth Taylor by Andy Warhol in November, just six years after he bought it for about £2m. It is the kind of return that would make even the most successful hedge fund manager envious.

Newspapers are full of such tales. Newly made millionaires in newly rich economies such as China and Russia are scrambling to secure cultural assets. Christie’s, the auction house, reported record sales of Asian art to buyers from China and India last year. Sotheby’s, its rival, claimed 2007 was its best-ever year for Russian art sales. But it is striking that in spite of reports of record price rises, investment banks such as JPMorgan do not designate art as an investment class.