Estate oddity! Napoleonic fort near Portsmouth on sale for £3m+ after years as a luxury island retreat

Where others saw an old hunk of granite long beyond its heyday, businessman Mike Clare spotted opportunity.

In 2008 he sold his company Dreams for £200 million, and over the following years decided to make a trio of unusual real estate investments known collectively as the Solent Forts.

Now one of them, Spitbank Fort off the coast of Portsmouth, is up for sale, and it’s accepting offers in excess of £3 million.

The structure features 15-foot-thick granite walls with armour plating, and is the result of a 15-year project undertaken in the 1860s to defend the Solent from a possible French naval invasion.

That never came to pass, and Spitbank Fort – along with the nearby No Man’s Fort and Horse Sands Fort – were abandoned.

But in the hands of Mike Clare, the three outposts have undergone a transformation into luxury resorts only accessible by boat, with each essentially acting as its own private island.

Spitbank itself boasts a roof terrace and eight luxury guest suites, with amenities including a hot pool, sauna and wine tasting room.

It also features four function rooms, the largest of which, Crow’s Nest Bar, offers a roof terrace, sun decks and panoramic views across the Solent.

After years welcoming paying visitors to the island, Mike is now on the hunt for a buyer with the help of Toby Turnage and Edward Cunningham at Knight Frank.

Toby said: “The size of the forts is amazing.

“They’re massive – incredibly well-built and engineered, especially given that they’ve been sitting in the middle of the Solent for the last 160 years.”

“I think having Spitbank as a private residence would be the coolest thing.

“Put a flag on it, claim independence and have your own little island. That or an experiential offering, a place for people to go and stay.

“You’re not going to find anything else like it.”

• solentforts.com