The future owner of this Grade-II listed Bull Sand Fort will need a private boat to reach its secluded spot in the Humber Estuary in northern England.

Originally built during WWI, the floating structure didn’t come into use until WWII – when it protected the approach to the estuary with guns and an anti-submarine net. It also had enough space to garrison 200 men.

Bull Sand Fort was decommissioned in 1956 and, as can be seen from its weathered concrete exterior, it needs serious refurb work (for whatever its future adaptive re-use might entail). But there’s plenty of space to work with, including three floors below sea level and a two-storey observation tower.

The mainland is three miles from the apocalyptic military relic, but the fort is somewhat self-sufficient with an artesian well. Bidding starts at £50,000, and Savills is the auctioneer.

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