A Victorian sea fort which was due to be auctioned has been sold privately at the last moment for more than £1m.
Spitbank Fort was built to defend the Solent and mainland from French attack and was due to be sold on Wednesday.
Described by its owners as the "ultimate entertainment centre" for functions, it had a guide price of between £600,000 and £700,000.
Details of the new owner of the 50-room island property one mile (1.6km) off the coast have not been disclosed.
Auctioneer Rob Marchant said an it was an "exceptional offer".
He added: "The interest we had was enormous, with inquiries as far away as Hong Kong and the United States.
"It was a pity the fort didn't go under the gavel, but the important thing is that it has been sold.
"It's not every day you get to buy a man-made island with privacy, security and space, with 50 rooms steeped in military history and some of the finest panoramic views in the UK."
The fort was sold by entrepreneurs Neale Brickwood, Paul Holland and Ian Price who bought it for an undisclosed sum in July 2005.
They had been holding functions at the 148-year-old venue, which is licensed for up to 500 visitors and also has permission for a casino.
Mr Brickwood said: "We've had a great four years owning Spitbank Fort and establishing it as the ultimate entertainment centre in the middle of the Solent, but when we received the offer for more than £1m we felt we had to take it."
Spitbank is one of a series of forts in the Solent.
Mr Marchant said it reportedly cost nearly £120,000 to construct between 1861 and 1878 and was one of Palmerston's Follies, a series of land and sea-based forts designed to repel French warships, but was never put into action.
Its walls are 15ft (4.5m) thick at basement level, with 35ft (10.6m) thick sea foundations and a 8ft (2.3m) thick concrete roof.
During World War II it was installed with anti-aircraft guns to defend nearby Portsmouth harbour against German attack.
It was decommissioned in the 1960s and turned into a museum.
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