Tap above for a tour by ITV Meridian reporter Chlöe Oliver who has been delving into the history of the trio of fortresses between Hampshire and the Isle of Wight.
Three historic forts off the coast of Portsmouth have been put up for sale.
Spitbank, No Man's and Horse Sand Forts were built by Lord Palmerston during the 19th century to protect Portsmouth's great Naval base from a possible attack from Napoleon III. But the forts were never used in anger as the threat never materialised.
Ten years ago, they were taken on by Buckinghamshire entrepreneur Mike Clare who set up Dreams bed company. He took over renovations but now is putting them on the market to buy, either individually or as a trio.
The structures were originally built 160 years ago to repel the threat of a French invasion. They're almost unrecognisable today with hotels, bars, a lighthouse, helipads and hot tubs.
Interview below with historian and archaeologist Stephen Fisher who is also part of the Palmerston Forts Society.
Although they were never used during the 1860s and saw little action during the First World War, during the Second World War, the forts were manned by soldiers and were three of around 50 land and sea forts across Portsmouth and Gosport which, if nothing else, seemed to serve as a deterrent to any potential enemies.
All three of the forts were decommissioned after World War Two. Horse Sand Fort appears almost as it was left in the 1860s after plans to turn it into a museum were put on hold.
In the depths of Horse Sand Fort, current owner Mike shows us the remarkable Victorian engineering which is still used to this day. Each fort has an Artesian well which supplies pure, fresh water which runs under the Isle of Wight and comes from France.
The other two for sale,No Man's Fort and Spitbank Fort, have been redeveloped into luxury hotels.
No Man's Fort price
Spitbank Fort price
Horse Sand Fort price
To value fort is no easy exercise but if you compare it to London properties and country houses and use measure of pounds per square foot these properties are remarkably good value for money.