Is this Britain’s most secretive mansion? The fortress on a private island – with 20 cannons out the back

Is this Britain’s most secretive mansion? The fortress on a private island – with 20 cannons out the back

Hidden behind 100-foot granite walls on a secretive private island off Sark lies a sprawling £60 million fortress with cannons, swimming pools – and a long-running feud

Published: June 18, 2025 at 1:52 pm

Off the coast of Guernsey in the Channel Islands is the stunning car-free island of Sark – but just 80 metres from Sark is another island, which has drawn much intrigue and speculation over the last few decades, since it was bought by the Barclay brothers.

The 74-acre private island location was perfect for these privacy-loving British billionaires. Brecqhou is now home to a mock-Gothic castle, designed by Quinlan Terry, the neoclassical architect behind the 1980s refurbishment of 10 Downing Street, the library of Downing College, Cambridge, and the addition to Brentwood cathedral in Essex. The £60 million mansion is known as Résidence des frères Barclay – or 'Fort Brecqhou', and is complete with 100-foot granite walls, battlements, two swimming pools and a helicopter pad.

In 2006, Professor David Watkin described Résidence des frères Barclay as “the largest house built in Britain for at least two centuries” in his book Radical Classicism.

A big renovation job

When they bought the island of Brecqhou in 1993 for £2.3 million, the costs started piling up pretty quickly. Not only did they have to build a house on a remote island (famously no easy feat), the Barclay Brothers also had to restructure the entire landscape to protect it from the brutal winds. According to the Guardian, “Vast sections of the windswept, cliff-shorn island were cleaved off, lakes created and strategic hill ridges elevated such that the profile of Brecqhou was transformed”.

The previous manor house that was on the island was deconstructed, and in its place, a new concrete palace that used two types of Spanish granite to create its Gothic look.

Stonework above the front door supposedly displays the family coat of arms and the motto “Aut agere aut mori” (Either do or die), thought to be associated with Scottish Barclay clan history.

At the back of the house, there are 22 cannons – fired to mark special occasions.

Brecqhou Castle gardens (credit: Getty)

The secrets of Résidence des frères Barclay

Rumours and secrecy have swirled around Résidence des frères Barclay since it was built. A couple of the more extreme rumours included the presence of a nuclear bunker, and the roads were all made of marble.

When the castle was being built in the 1990s, workmen were believed to have laboured through the night, each having signed a non-disclosure agreement. Everything is kept under wraps.

Sark vs Barclay brothers – an ongoing feud

Brecqhou is politically part of Sark, but its private owners have challenged this fact. While cars and helicopters are banned on Sark, the Brecqhou owners use both on their island – just one of many disagreements between the government of Sark and the Barclay brothers.  

The brothers protested the rate of property tax on the island, challenged the Sark government on its governance, pulled investments from the island of Sark, and took Sark’s government to the Supreme Court, in a challenge which was dismissed. In 2012, BBC Radio 4 dedicated part of its Today programme to the Barclay brothers’ role in Sark. There have been endless disagreements between the Barclays and the Sark government (and Sark locals) during the Barclays’ ownership of Brecqhou.

Who owns Brecqhou in the Channel Islands?

Sir David and Sir Frederick Barclay bought the island of Brecqhou in 1993 and went on to build a £60 million Gothic-style mansion there. David died in 2021, leaving his brother as the sole tenant of the island.

After taking on ownership of Brecqhou, the brothers faced legal disputes with the government of Sark, and expressed a desire to make Brecqhou politically independent.

Who are the Barclay brothers?

Sir Frederick Barclay and his late identical twin brother Sir David Barclay, commonly referred to as the Barclay Brothers. They own The Telegraph and The Spectator through their company Press Holdings, as well as the online retailer Very and the delivery group Yodel.

Their early wealth came from redeveloping London boarding houses into hotels, and building stakes in businesses such as breweries and casinos. They bought the Ritz Hotel in 1995, as well as a shipping company and a motor retail chain. They were knighted in 2000 for their philanthropic support of medical research.

While Frederick Barclay topped the Sunday Times Rich List in 2023 with £6.4 million, he has not appeared on the list since then, due to the lack of “robust financial data” to estimate his wealth.

The island of Brecqhou, the home of the Barclay Brothers next to Sark, Channel Islands
The island of Brecqhou, the home of the Barclay Brothers next to Sark, Channel Islands (credit: Getty Images)

Can you visit Brecqhou?

In theory, Brecqhou is visitable – although public visits are only possible by prior arrangement. And honestly, we're not sure how you'd go about asking.

As part of the research into his book Treasured Islands: Journeys round the Inhabited Islands of Great Britain and Northern Ireland, John Chatterton was granted permission to visit Brecqhou, albeit just for 10 minutes. Fortunately, once he had landed he ended up being able to spend about an hour exploring the island. He was also able to visit Jethou, another private island off the coast of Guernsey. Jethou is currently leased by businessman Sir Peter Ogden, a founder of Computacenter and owner of MotorSport Vision, which runs Leicester’s Donington Park circuit.

"Even though I was told I could only have 10 minutes there the estate manager was so warmly welcoming that we chatted away and drove away in a golf buggy across the Island for well over an hour,” Chatterton told the BBC. He was restricted on what he was able to say about the visit, however, and was unable to take any photos while he was there.

An aerial view of Brecqhou (credit: Getty)
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