British billionaire named as one of five passengers on missing Titanic tourist sub as rescue mission launched

Harding's stepson Brian Szasz confirmed he was missing on social media.

He wrote on Facebook: "Thoughts and prayers for my Mom and Hamish Harding."

The stepson added: "Hamish Harding my stepfather has gone missing on submarine thoughts and prayers."

Rescue crews have been searching the Atlantic Ocean after the tourist vessel vanished.

It costs around £200,000-a-head to embark on the tourist voyage.

Harding, who is CEO of Action Aviation in Dubai, revealed he was going to join the Titanic tourist trip yesterday.

He wrote on Instagram: "I am proud to finally announce that I joined Ocean Gate for their RMS TITANIC Mission as a mission specialist on the sub going down to the Titanic.

"Due to the worst winter in Newfoundland in 40 years, this mission is likely to be the first and only manned mission to the Titanic in 2023.

"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."

Ocean Gate, one of the companies which provides the Titanic tourist service, confirmed a major search had been launched.

A spokesman for Ocean Gate said: "We are exploring and mobilising all options to bring the crew back safely.

"Our entire focus is on the crewmembers in the submersible and their families.

"We are deeply thankful for the extensive assistance we have received from several government agencies and deep sea companies in our efforts to reestablish contact with the submersible.

"We are working toward the safe return of the crewmembers."

The Boston Coastguard is leading the search for the vessel.

Lieutenant Jordan Hart, from the US Coast Guard in Boston, confirmed to American outlet CBS News that personnel were “currently undergoing a search and rescue operation” off the coast of Newfoundland.