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One lazy Sunday afternoon, you tag along with a friend on a time-wasting, energy-sapping, tat-tastic trip to a car-boot-sale, where, would you believe it, you happen upon a lost masterpiece for £40. This notion is, of course, a cliche.

But it does happen - rarely, for sure, but often enough to give Antiques Roadshow and Cash in the Attic their appeal. As the big finger in the original National Lottery ads pointed out, "It could be you".

The American painter and collector Rick Norsigian thought it was him when he bought 65 glass-plate negatives for $45 (£29) at a Fresno garage sale in 2000. "Hmm," he must have thought to himself, "is this not the 'lost' collection of that great American photographer Ansel Adams?"

Keen to turn his newly-found cache into cash, Norisigian went about trying to authenticate the negatives as the work of Adams. He succeeded, after enlisting the help of some people he considered to be experts.

But his claims have been refuted by the Adams Family Trust, which says the pictures were not taken by Ansel Adams. Others agree: perhaps the most damaging dissenting voice is that of Wyoming-based art consultant Robert C Moeller III, who had been on Norsigian's original list of expert authenticators.

The dispute will now be settled in court. But Norsigian is not to be deterred by such a minor inconvenience; he's selling them as prints anyway. You can buy them on .

But first you have to agree to a pop-up disclaimer that reads:

Now that is unusual. The punter is being asked to pay a price based on the prints being authentic; but, should they prove not to be the work of Adams, too bad. Isn't the point of buying art from a dealer that they have done the legwork and authenticated the provenance of the artwork? And if it turns out not to be by who they said it was by, isn't it money-back time?

The value of an artwork is entirely dependent on who created it: the bigger the name, the bigger the price. Which makes authentication crucial and adds dramatic spice to any art purchased from a third party. It is often difficult to be 100% sure. It is a risky business which makes for good stories, whether that's in the recent series of Sherlock Holmes or at the National Gallery, where is currently on.