Waiter, this £18,000 1961 Petrus is fake

It was a moment to make the most experienced sommelier gasp with horror.

Normally when a favoured wealthy customer orders a magnum of Pétrus 1961, appreciative purrs of pleasure are expected to follow.

Not just from the drinkers. There will be a profit of several thousand pounds on a bottle costing as much as a large family car.

But this time the usually exquisite claret was returned untasted with angry accusations that it was a fake.

This was the hugely embarrassing scene at the Michelin-starred Zafferano in Knightsbridge earlier this month when a party of British and Italian diners asked for the 1961 - regarded as one of the finest wines ever made - to go with their meal.

At £18,000 it was among the most expensive bottles on the wine list, described by one reviewer as "awesome in its density, richness and concentration".

But the customer refused to touch it because the cork was not stamped with the standard mark of provenance proving where and when it was made.

Zafferano's general manager Enzo Cassini admitted it was an awkward and unprecedented situation. "Yes, the customer was cross. He had a problem because when he saw that there was no mark on the cork he didn't want to drink it any more. He said: 'this could be a fake.'

"The bottle was perfect, there was nothing to think it wasn't genuine. I tasted the wine and it was off anyway. It was a big disappointment for the customer because he had brought over a friend from Italy. We have had to write off the Pétrus. As they say, stuff happens."

But the restaurant was so alarmed by the possibility that it was the victim of a fraud that it called in the "Pétrus police" from Corney & Barrow, an upmarket City wine bar chain who also act as agents for Pétrus n Britain.

The company has accumulated photographic records of every surviving bottle still stored at the 28-acre vineyard to counter the growing phenomenon of wine fraud.

The allegation was regarded as so serious that Corney & Barrow despatched its managing director Adam Brett-Smith to investigate-Although there was no evidence the bottle was a fake, Mr Brett-Smith was unable to provide a definitive answer.

The company said: "What we told the restaurant and later confirmed in writing is that it is impossible to confirm 100 per cent the authenticity of a wine pre-1964." Before then the vineyard was run as a family concern by the former owner Madame Edmond Loubat with only limited record keeping and no cork stamps.

Corney & Barrow now insist that every empty bottle of Pétrus is destroyed after the contents have been drunk to stop it being refilled with an inferior, fraudulent wine.

The row at Zafferano had a happy ending. After calming down the customer ordered an alternative - a magnum of Mouton Rothschild 1945 at £20,000. This time it got drunk.

But for Mr Cassini, it was a case of once bitten, twice shy. "I wouldn't buy any more wine of that calibre. It is a big risk to take. Only a few customers go for a wine like that. You can have fantastic experiences with younger wines from the Eighties or Nineties. Is any wine really worth £20,000?"