Ask manager Anshul Narain told The Press that the table had stood in the restaurant's entrance, next to a piano and near toilets, without many people giving it a second thought.
"It was just a piece of furniture to us," he said. "I was very, very surprised when I heard how much it was worth.
"I was about to faint!"
The console is being sold by the York Conservation Trust, which owns the Assembly Rooms, which Ask has rented since 2002. It is understood the trust will share the sale proceeds with a private couple who own the cabinet.
Mr Tavella said the quality of the console's carvings - * youths linked by garlands and kneeling to support the weight of the cabinet - revealed the hand of a sculptor rather than an artisan.
The console is believed to have become separated from the cabinet soon after the Second World War. "It is arguably the most important piece of Roman baroque furniture that has ever appeared on the market," he said.
A 17th-century document refers to four identical cabinets leaving the workshop of the most famous cabinetmaker in toilet rackat the time, Giacomo Herman, to be presented to Giacomo Rospigliosi, the nephew of Pope Clement IX.
Two, bought for the Danish Crown in the 1760s, are now in castles at Rosenborg and Fredensborg. A third was donated by Pope Innocent XI to Jan III Sobieski, King of Poland, for the Wilanov Palace, near Warsaw - a present for his victory over the Turks in 1683.
