An abandoned bomb-proof fort on the River Thames in London which dates back to the 19th century has just gone onto the market. 

The gun emplacement tower, known as Grain Battery Tower, was built off the coast of the Isle of Grain where the Thames meets the North Sea in 1885 as part of a chain of coastal defences built because of the continuing threat of invasion from the sea following the Napoleonic wars. 

With a £500,000 price tag, the property has already generated a lot of interest from potential buyers considering converting it into a recording studio, hotel, houseboat community and seven bedroom luxury home.