The friend of British billionaire Hamish Harding who is thought to be on board a submarine that has gone missing while on a dive to visit the wreck of Titanic has spoken out and revealed the last text he received from him.

A search and rescue mission continues to be underway in the north Atlantic Ocean after coastguards lost contact with the 21-foot vessel on Sunday.

Those onboard, including Harding and four others, have enough oxygen in the submarine until Thursday, it has been said.

Harding,  the chairman of aircraft sales firm Action Aviation, wrote in a Facebook post on Saturday that he was joining the latest Oceangate expedition to see the Titanic.

Colonel Terry Virts, a friend of Harding, appeared on Tuesday’s Good Morning Britain with Richard Madeley and Susanna Reid, and spoke about Harding’s expertise.

He began: ‘We don’t really talk about risks, it’s known he understood the risks for sure, there’s no doubt about that.’

Hamish Harding wrote on Facebook he was ‘proud to finally announce’ he would be joining the expedition (Picture: Facebook)

He went on to reveal the last text he received from his friend, which said: ‘”Hey, we’re headed out tomorrow, it looks good.”

‘The weather’s been bad so they were waiting for this.’

Colonel Virts elsewhere recalled Harding’s world records, including for the longest time spent at the deepest part of the ocean, which was earned when he spent four hours and 15 minutes at the bottom of the Marianas Trench with fellow record-holder Victor Vescovo in March 2021.

‘We talked quite a bit about the risks and the different things that they were going to be able to do, and he was very excited about it.

‘They’re actually going there for a fun trip but doing serious science also.’

Colonel Virts recalled the last message Harding sent him (Picture: ITV)

He continued: ‘So it wasn’t just a fun trip, they were doing real exploration for all of humanity.

‘The Titanic is not only important to Britain, it’s important to everybody.’

Colonel Virts added that Harding’s family are ‘all together at his house’, requesting privacy but ‘appreciative of everybody’s support’.

He continued by saying Harding is ‘extremely proud’ of the UK, and ‘carries the flag on all these adventures that he does.’

Good Morning Britain airs weekdays from 6am on ITV1.

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‘He was very excited about it.’