There is a catch, of course, as what you see is not necessarily what you get. You may have bought an Antony Gormley, but then again you may have bought an unknown artist working in the style of Gormley. All signatures are out of sight on the back of the postcard-sized works of art - that's the "Secret" - and you won't know what you've picked until you have handed over your money and the exhibition has come to a close.
Only three people, including the curator Diana Charnley, are in the know, and they have been sworn to secrecy. And even if they could give out any clues there'd be little point, according to Charnley, as the artists' styles are rarely typical. "I've been quite surprised by some of the work that has come in," she says, "as it is not necessarily work you would associate with a particular artist who has been working for maybe 10 or 20 years."
A handful of the works will, however, be instantly recognisable, says Charnley, but for the most part punters will have to make an educated guess or simply buy from the heart. "It raises lots of serious questions about art in general," says Charnley, "because, as a potential purchaser, you are forced to buy an image because you like it, irrespective of the person who made it."
The fundraising event was first dreamt up by the RCA six years ago as a means of funding bursaries, lectures and student end-of-year shows. Absolut Vodka covers the costs so all the money spent on the art is ploughed back into the college. Jill Knock, the veteran buyer who now has 15 of the postcard miniatures to her name, believes it helps to have an eye for the style of the artists you're looking for. "I've got some Bellanies, a Maria Pacheco, a Bryan Kneale and a Nicola Hicks," she says. But that's not to say that all the most valuable works get red-stickered in the first five minutes. In some years, big-name postcards are left hanging around unsold until the 11th hour, if they get sold at all.
"I love the excitement of it," says Knock, explaining her addiction to the sale which sees her coming back year after year. "I love the fact that you have this little gem of a picture. It's a little piece of somebody - perhaps of an artist who is well known, but who I would never normally be able to afford."
Last year, armed with vacuum flasks, deck chairs and thick wool blankets, the most determined of the art shoppers started queuing at 6pm the day before the opening. By eight the following morning, the queue was snaking up the road and round the corner.
This year there will be up to 2,000 works by 400 artists, ranging from household names to students. A limit of six postcards a head means that there's no chance of striking lucky by doing a blanket buy, but a list of all the artists taking part helps buyers to know what to look out for.
Albert Irvin, who has submitted four works this year, is one artist who makes no attempt to fool the viewer by camouflaging his work. "There are a lot of students who do pastiches of different people's style. But I'm not playing games. I just do a small painting," he says.
Irvin, who has contributed something every year since the show's inception, believes that you don't have to strike gold to be a winner. "You can't make a mistake," he says. "At the very least, you'll like it, or you wouldn't have bought it in the first place. On the other hand, you could end up with what turns out to be quite a valuable work for peanuts."
Absolut Secret, sponsored by Absolut Vodka, Royal College of Art, Kensington Gore, London SW7 (information hotline: 020-7590 4186). Viewing only, Thursday to 1 Dec, 10am-6pm. First day of sale 2 Dec, 8.30am-8pm, until 5 Dec, 10am-6pm