“It’s a huge trend,” Barber said. “The wealthy are looking for an escape. Often they want to get some sense of a back-to-basics lifestyle and learn the skills of our ancestors, like how to hunt and cook their own food.

“For others, it’s ‘braggability’. They want to use their money to open doors that normal people can’t and to tell their friends all about it,” he said. “If you’re in the 0.01 per cent, you are going to be a competitive type of person.”

These are no ordinary holidays. Recent trips Barber’s firm has arranged include snow leopard spotting in India, living with the San people in Botswana and diving with sharks in the ‘sardine run’ off the coast of South Africa.

Barber said his company had arranged 80 sabbatical trips lasting at least a month over the past six years, with a significant jump in bookings over the past year. High-end travel agents in the United States have reported a similar trend and also launched bespoke sabbatical booking services.

Barber said most sabbaticals are a month or two, but he had arranged a 12-month gap year for a 45-year-old billionaire who had recently sold his start-up and wanted “some time to reconnect with this family”. The trip cost well in excess of £1 million (HK$10.08 million).

The family visited 65 countries – from Mauritius to Bhutan, Antarctica and Greenland. “The guy was burnt out,” Barber said. “He wanted to see the world, get back to basics a bit and most importantly see more of his kids, who he hadn’t seen so much of when he was working to sell his company.”

A team of agents helped arrange the trip for the billionaire, including applying for visas and fixing up local guides in each country. Flights were the one thing Barber’s team didn’t need to worry about, as the family’s pilot flew them on their private jet.

Included on the family’s itinerary was tracking the elusive snow leopards of the Ladakh in northwest India. “They really wanted to see them, but didn’t want to wait there for 10 days and not actually see a snow leopard,” Barber said. So his team came up with a plan – they hired a team of local spotters and a helicopter to whisk the family from their luxury encampment the minute the leopards were spotted.

The family also spent time with the San indigenous hunter-gatherers in Botswana, where they learned how to hunt and cook their own food, and live without money. They also dived the sardine run off the coast of South Africa, where billions of sardines migrate up the east coast attracting huge numbers of predators, including sharks and dolphins.

They were joined in the dive by a professional documentary team, who helped the family film their experience. “They then showed them how to edit the rushes and make their own mini-film,” Barber said. “An overwhelming element is the super-rich want to learn new skills. Sitting on a superyacht in the sun is pretty old-school these days – people want to have adventures and learn new things.”

As well as arranging the visas, logistics, guides and activities, Barber’s firm built a website for the family so that their friends back home could keep tabs on them.

Barber said planning for the trip started with: “A big map of the world in our conference room in Battersea [south London]. Our experts put pins in where they thought some of the best options were and we put a list of suggestions to the family.”

He declined to identify the family, but said the father who instigated the trip was an “extremely nice, humble, pretty unassuming guy who happens to have untold billions”.

Barber said the super-rich often take their families on sabbatical to show them “how real people live” and to learn the power and importance of money. “They want their children to see some real life, but in a safe and secure way,” he said.

The super-rich sabbatical trend has also been spotted by high-end travel agents in the US. Jack Ezon, president of Ovation Travel Group in New York, said the number of sabbaticals had “grown exponentially in the last couple of years”. He said his firm arranges 50-60 sabbaticals about a month long in a year, and 5-10 whole gap years.

“It’s a way to restart or refresh your life,” he said.

Ezon said many of his clients booking long sabbaticals are entrepreneurs who have sold their businesses and are looking for a proper break. “It is often tech guys who have floated or sold their companies and are thinking ‘I have a two-year non-compete clause, what am I going to do with my time?’” he said. “For others it is often when their kids are about to go on to college or high school, and they suddenly think ‘I need to really be spending time with them’.”

A US executive living in Mexico, who asked to remain anonymous, told the Guardian he was setting off on a seven-month sabbatical with his wife and two children next month. The family are planning on driving from Punta Arenas, at the very southerly tip of Chile, back to their home in Mexico.

"We've shipped our vehicle down to the very south of Chile, and fitted it out for an extreme adventure, with a tent on the roof and full suspension," he said. First the family will head to Antarctica, before driving up the Andes, stopping off to trek to Machu Picchu in Peru and to dive the Galapagos Islands.

“My wife and I decided that we had to do this now, to spend some intensive time with our kids before it was too late,” he said. “My eldest is about to turn 13 and the youngest is nearly 10.”

The kids will miss more than half a year's schooling. The executive and his wife, who both have experience teaching, plan to home school or - "van school", as he puts it - the children.

Children’s education is often a stumbling block in people’s sabbatical plans, but there are a number of ways round the problem if you have the money, said Ezon. “We have a roster of teachers and retired teachers that we can suggest to families to take with them on their trips,” he said.

He said long trips can easily become very expensive, but “these are very, very wealthy people and they can afford it”. “It could be a couple of million dollars to take your family around the world with a teacher in tow.”

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