A historic island fort is being sold for less than the price of a one-bedroom flat in London. Stack Rock Fort, off the coast of Milford Haven in Pembrokeshire, was built to defend Britain from an invasion from France's Napoleon III. Made up of three floors with spiral staircases leading to each one, with cannon rooms, former sleeping quarters, the island provides a 360-degree view of the Haven waterway. The average cost of buying a home in London is £471,944 and the average cost in Wales is £152,999, according to the UK Land Registry.