Medway’s most unusual property, Grain Battery Tower,an abandoned fort in the middle of the Thames Estuary, has been sold for a sum in the region of £400,000.

The undisclosed new owner of the 19th century military installation will have the enviable address of No 1 The Thames.

The property built off the coast of The Isle Of Grain has been on the market for the past decade and had an asking price of £500,000.

Potential uses suggested over the years include a seven-bedroom mansion, nightclub, hotel, outdoor pursuit centre, gentlemen’s club or casino.

It is estimated that about £1 million would have to be spent to make it ship-shape .

Nigel Day, of River Homes, London-based waterside property specialists, said: “An offer has been accepted, but the buyer does not want any publicity until the conveyancing and contracts have been drawn up.

“The property has attracted a huge amount of interest since going on the market earlier this year.

“It is fair to say that the interested party is a relative newcomer.”

It was bought by builder Simon Cooper about 12 years ago who had intended to convert it into a family home.

Mr Cooper, from south east London, said: “I did spend a bit of money making it habitable and did live there for a while. But I soon realised it was more of a bachelor pad,”

Estate agent Jonathan Hacker said the fort came on to their books by chance as Mr Cooper was working on one of their offices

Mr Hacker said: It is one of the most unusual properties we have had. We are more used to dealing with house boats on the Thames. I think its main appeal was its potential.

“It went online and suddenly sparked amazing interest both in the media and with potential buyers.”