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Disused fort on River Thames up for sale

13 August 2014 Last updated at 14:17 BST

A seven-bedroom mansion, with sea views and in commuting distance of central London, is on the market for £500,000.

This might sound like a bargain, but there are a few drawbacks.

You can only get to No 1 The Thames when the tide is low or if you have a boat as it is situated in the Thames Estuary.

BBC London's Gareth Furby took a tour with estate agent Nigel Day and spoke to its current owner Simon Cooper, from Eltham, south-east London.