A Chinese altarpiece that was being used as a table lamp in a Cornish home has sold for £25,000 – 40 times its estimated price.

The damaged porcelain piece was listed at £400 to £600 when it went on sale at The Penzance Auction House this week. But, thanks to hectic bidding from the other side of the world, it ended as the sale's star performer.

Auctioneer David Lay spotted the work of art at the home of a Mid Cornwall customer, where it was being used as a table lamp on a coffee table.

"My eye was first caught by the light shade over it, but on closer inspection I found this really interesting altarpiece beneath the shade," he said.

"It was clearly damaged and incomplete, but I still thought it had a lot of potential – just nowhere so much as eventually turned out to be the case."

An expert said the damage to the piece would bring its value down, so the auction house gave it a lower estimated price.

"Nine times out of ten we come pretty close with our price estimates, but I am delighted to confess that we got this one spectacularly wrong," said Mr Lay.

"We had five phone lines open for the bidding. There were some 30 people registered to bid, and most of them were from mainland China.

"It was an amazing experience, as the price soared."

Eventually the Chinese bids were beaten and the piece was sold to a specialist London-based dealer.

Mr Lay said the previous owner was "absolutely delighted" when she heard the news.

The late-18th century altarpiece was in the form of a Tibetan "stupa" – a mound-like structure containing Buddhist relics, used by Buddhists as a place of worship.

The 22cm piece was decorated in coloured enamels with lotus flowers, scrolls and grotesque masks on a yellow and puce background.