Spot the masterpiece?

So you think you know your art – but can you tell your £15,000 Peter Doig from your £40 student artist? Arifa Akbar reveals all

The country's biggest art lucky dip is back, in the shape of the Royal College of Art's "Secret" exhibition, at the end of next month.

Art-lovers can choose to buy one of about 2,000 postcards produced by the country's most established artists, fashion designers and photographers, including David Hockney, Damien Hirst, Tracey Emin, David Bailey and Zandra Rhodes, as well as unidentified student artists, for £40. What makes the show so exciting is that the signature on the back of the postcard is only revealed after it has been bought.

Alongside an exclusive preview of some of this year's postcards on sale (pictured), keen-eyed aficionados are invited to guess which image amongst them is by the artist Peter Doig. The postcard in question was bought by one lucky recipient for £35 in 2000. The postcard is up for auction at Sotheby's with an estimate of up to £15,000 on 27 October.

Also in this collection are cards from past years by Paula Rego, Peter Blake, Hirst, Emin and Paul McCartney. Can you spot them? This year's sale will include contributions from Yoko Ono, Emin, Olafur Eliasson, Bailey, Paul Smith, Grayson Perry and the Clash bassist Paul Simonon, among others.

For more details on the exhibition, visit www.rca.ac.uk/secret .