Inside Britain's most expensive home: Channel 4 show follows final stages of Mayfair mega mansion's £68m renovation

Phones 4u founder John Caudwell's new-look Mayfair home has London's largest private ballroom after Buckingham Palace.
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The renovation of an extraordinary home carved out of two mega mansions in the heart of Mayfair has been featured in a one-off documentary, Britain’s Most Expensive Home: Building for a Billionaire, on Channel 4.

The property was bought in 2012 by businessman John Caudwell, 67, who sold his Phones 4u chain for just under £1.5 billion in 2006.

"I was looking for anything I deemed 'good value', regardless of size or price," says John during the programme. "So I bought it, I think it was £87million."

Around four years ago, John decided to embark on a total renovation of what was, he says, a "tasteless gold palace".

Watch your step: on the third floor, a river with handpicked African Cichlid fish flows through the Thai-style dining room
Matt Writtle

Watching the renovation unfold

The Channel 4 team join the build for its final stages: a point when the project - which has already run over on time - is £55 million over budget, too.

"The budget has always been irritating, because the budget went up and up and up and we got to this huge budget of where we are now which is over £65 million," says John.

"A big increase from the £10[million] I originally conceived, somewhat naively," he adds.

Tonight's show follows the workforce in the final three months of the project, as they try to meet the new deadline of John's birthday on 7 October.

A burst pipe just six weeks before John intends to move in almost derails the entire renovation, and self-described micro-manager John is unimpressed with the progress he sees on his frequent visits.

See inside: Britain's most expensive home

Inside Britain's most expensive home: a £250m mega-mansion in Mayfair

A superhome is born

The super-home has 110 rooms; spanning 43,000sq ft - which is roughly the average size of 55 London flats — and more than twice the size of the Royal Albert Hall.

John's friend Dawn Ward, an interior designer and one of the original cast members of ITV reality series The Real Housewives of Cheshire, has spent four years designing the house interiors with her team.

Speaking of the £65 million budget, Dawn says: "It's astronomical but honestly, for the quality and a house of this size, it's actually quite a tight budget."

More than a thousand pieces of furniture have been bought for the home at a cost of around £6 million.

Beauty in the basement: on the wall behind a 40-foot swimming pool is a volcanic lava installation which cost £200,000
Matt Writtle

Bond-style gadgets

A real showstopper gadget is the automated eight-car "stacker", which can summon any of John's impressive car collection at the touch of a button.

On installation, the builders reveal the steel frame alone cost £500,000 and the room for error is just 10 millimetres on either side, meaning if it doesn't fit it would have to be returned to the manufacturers — in Turkey.

Inside, senior designer Jenny explains that gold leaf is being installed in the master bedroom. Overall 20,000 sheets of gold leaf are used in the home, at a cost of £28,000.

The bed in the master suite is an "emperor-size bed" measuring two metres by two metres, which means you can "starfish and you don't touch the person next to you," she says.

In the basement, on the wall behind a 40-foot swimming pool, is a spectacular volcanic lava installation which cost £200,000.

Other features you might not expect to find in this historic London enclave include a Thai-themed dining room —​ John's favourite food — with a river flowing through its centre filled with handpicked African Cichlid fish, all set beneath a preserved 15-foot cherry tree adorned with pink silk blossom.

Cavernous space: the ballroom is said to be the largest private ballroom in London after Buckingham Palace
Matt Writtle

Grand plans

John Caudwell's main residence is a 12-bedroom country house in Staffordshire and, along with other homes around the world, he also owns a 73-metre yacht which he bought at auction for the “bargain” price of £35 million.

He will use his Mayfair home when he needs to be in London, but he has created zones within the house that can be used for his charitable foundation, Caudwell Children, which supports disabled children and their families.

He will throw gala evenings, charity balls and hold meetings at the newly revamped property.

As the documentary makers, builders and site managers pack up, John is preparing for the 30 or so close friends arriving that evening to celebrate his birthday.

"I've got this spectacularly perfect house," says John, "If someone spills some red wine on the carpet I'm going to just look away."

Britain’s Most Expensive Home: Building for a Billionaire aired on Channel 4 at 9pm on 5 February