Missing British billionaire Hamish Harding has a Guinness world record for the longest duration spent at the bottom of the sea.

The London-𝐛𝐨𝐫𝐧 adventurer set it in 2021 after diving in a submersible to the deepest place on Earth, the Mariana Trench, and traversing it for four hours and 15 minutes.

It was one of three world records the 58-year-old has earned. He set another one for the longest distance – three miles – covered at the bottom of the ocean. His first was set in 2019, for the fastest circumnavigation of the Earth via North and South Poles in a Gulfstream 650ER business jet. And last year he went into space.

Before setting off on the Titanic tourist submarine, which is now missing, Mr Harding told his social media followers: ‘A weather window has just opened up and we are going to attempt a dive tomorrow.

‘We started steaming from St Johns, Newfoundland, Canada, yesterday and are planning to start dive operations around 4am tomorrow morning. Until then, we have a lot of preparations and briefings to do.’

An employee of Mr Harding last night revealed the billionaire had wanted to go on the trip for ‘a long time’ – adding there is still ‘plenty of air’ onboard.

Missing British billionaire Hamish Harding (pictured) has a Guinness world record for the longest duration spent at the bottom of the sea

Before setting off on the Titanic tourist submarine, which is now missing, Mr Harding told his social media followers: ‘A weather window has just opened up and we are going to attempt a dive tomorrow.’ Pictured: Harding exploring the South Pole

The Action Aviation employee said: ‘There is plenty of air onboard still and there is plenty of time for a rescue to be carried out and we are waiting for the authorities to update us.

‘He is the only member of Action Aviation onboard and we are just waiting for updates. This is something Hamish had been looking forward to for a long time.’

The father of two is married to American national Linda Dunbar Szasz and they have two sons, one a fourteen-year-old boy named Giles.

The father – who is friends with astronaut Buzz Aldrin – said recently: ‘I used to read the book of Guinness World Records regularly as a 𝘤𝘩𝘪𝘭𝘥.

‘I always wondered how I could get into it. I did not think I could do it. And I didn’t want to do something stupid like setting a record for the number of ping-pong balls bounced in a day, or something like that.’

As the frantic search for the Titanic submersible was under way yesterday, family members asked for prayers for Mr Harding. The aviator, businessman and explorer is no stranger to perilous expeditions. He told an interviewer in 2021 how his submarine, Challenger Deep, sustained a damaged thruster during his journey to the ‘truly spectacular’ Mariana Trench, which lies seven miles below the surface of the Pacific Ocean.

He said: ‘The sub has many safety features, including four days’ reserve of oxygen, water and emergency rations.

‘The only problem is that there is no other sub that is capable of going down there to rescue you. It will take three years to build another one. So, having four days of supply doesn’t make a difference really. If something goes wrong, you are not coming back.’

An employee of Mr Harding last night revealed the billionaire had wanted to go on the trip for ‘a long time’ – adding there is still ‘plenty of air’ onboard

A social media post from Brian Szasz, the stepson of Hamish Harding

A submersible craft used to take people to see the wreck of the Titanic has gone missing in the Atlantic Ocean with its crew on board

This is the last sighting of the submersible, Titan, which was launched on Sunday. It is seen in a photograph shared by Mr Harding’s company

Mr Harding, who runs an aviation company in Dubai, also has the distinction of taking the oldest man – moon-landing astronaut Mr Aldrin, at the age of 86 – and the youngest, his 12-year-old son, to the South Pole, saying: ‘Buzz is an old friend of mine. We had always talked about going to the South Pole together and we finally did it in 2016.’

An only 𝘤𝘩𝘪𝘭𝘥, Mr Harding was 𝐛𝐨𝐫𝐧 in Hammersmith, London, in 1964, and has degrees in natural sciences and chemical engineering from the Cambridge University.

Last year, he was one of six astronauts to go to space on Blue Origin’s fifth human space flight aboard its New Shepard rocket.

Before another trip – to the North Pole two months before going into space – he said: ‘People, especially as they grow older, tend to give up on their dreams.

‘When I think of something unusual, I just try to find ways to make it happen.’

An employee of Mr Harding said: ‘He is the only member of Action Aviation onboard and we are just waiting for updates. This is something Hamish had been looking forward to for a long time’

OceanGate Expeditions is one of the only companies that offers the tours. Tickets cost up to $250,000