A tech entrepreneur bought a ruined Welsh island fort for £500,000, but after £2 million and a decade of work it became an 8,000-sq-ft off-grid home
In 2017, British tech entrepreneur Mike Conner bought Thorne Island, a ruined 19th-century fort off the coast of Pembrokeshire in Wales, for about £500,000 after seeing a video about the property online. At the time, the island had no electricity or running water and the fort had been left in a derelict condition after earlier attempts to revive it as a hotel failed. Conner, the former chief executive of software company Appsbroker, subsequently embarked on an extensive restoration of the Victorian fort, investing around £2 million in the project. The result is a property with more than 8,000 square feet of accommodation, five bedrooms and enough space to sleep up to 20 guests. The restored island has solar panels, battery storage, heat pumps and other infrastructure that allows it to operate independently of mainland utilities. In August 2025, Conner put Thorne Island on the market for £3 million through Strutt & Parker.
The military history of Thorne Island fort off the coast of Pembrokeshire
Thorne Island sits at the entrance to Milford Haven, a strategically important waterway leading towards the former Royal Dockyard at Pembroke Dock. The fort was constructed between 1852 and 1854 as Britain expanded its coastal defences amid concerns about the growing strength of the French Navy under Emperor Napoleon III. It formed part of the wider group of Victorian coastal fortifications associated with Lord Palmerston’s defence programme.The fort was designed to accommodate a garrison of about 100 men and featured a seaward-facing artillery battery. Its original armament included five seven-inch Armstrong guns and four 68-pounder guns, mounted in open positions behind the parapet. The landward side contained the defensible barracks, while the fort’s thick walls provided protection for the garrison and artillery. Thorne Island’s military role eventually ended, and in 1947 the fort was converted into a hotel. The property subsequently changed hands several times. It was sold for £275,000 in 1999, and in 2001 the Von Essen hotel group acquired the island with plans for a £4 million five-star hotel and a cable car linking it with the mainland. Those plans did not materialise. The island was sold again in 2011 and was put back on the market in 2016 before Conner acquired it the following year.
How Mike Conner restored the ruined fort into an off-grid island home
Conner’s restoration involved far more than renovating the interiors. When he bought the island, the fort lacked basic utilities and had suffered years of exposure to moisture. The isolated location also meant that construction materials and equipment had to be transported from the mainland by helicopter or boat. Contemporary reports say hundreds of helicopter trips were required during the restoration, while builders lived on the island for several years as work progressed.The restoration included extensive work to the historic granite structure, as well as the installation of modern water, heating, sewage and electrical systems. Reports have put the overall investment at around £2 million, with a substantial portion devoted to renewable-energy and infrastructure systems. These include solar panels, battery storage and heat pumps, while a dedicated sewage system and water-treatment infrastructure allow the island to function without conventional mainland utilities. Conner has described the project as a personal challenge undertaken after his career in technology. He bought the island after seeing it advertised as a derelict property and spent years turning the former military installation into a functioning private retreat. The restoration retained much of the original character of the fort, including exposed masonry, vaulted ceilings and the historic layout, while incorporating modern living spaces.
What the restored Thorne Island fort offers today for £3 million
The finished property now contains just over 8,000 square feet of accommodation spread through the restored fort. The current sale listing describes five bedrooms, an open-plan kitchen and snug, large reception and dining areas, a games room and a rooftop bar. Several rooms retain exposed traditional brickwork and vaulted ceilings, while large windows provide views across the surrounding waters. The island also comes with its own private jetty and helipad, allowing access by boat or air. A hydraulic crane is used to move supplies and equipment between boats and the island, an important feature given that Thorne has no conventional road connection to the mainland. The property is being marketed for private residential use as well as potential commercial or hospitality purposes.Thorne Island covers about 2.5 acres and the fort is a Grade II* listed building. Its location also places it within the wider Pembrokeshire coastal landscape, with the surrounding waters forming part of an area known for marine wildlife and historic shipwrecks. The island itself has therefore retained both its military heritage and its unusual position at the entrance to Milford Haven. After years spent turning a derelict Victorian fort into a functioning private retreat, Conner put Thorne Island on the market in 2025 for £3 million. The sale listing presents the property as a rare combination of historic architecture, private-island access and modern off-grid infrastructure, while leaving its next use open to whoever takes on the unusual Welsh property.
