UK billionaire Hamish Harding is one of the people on board a missing tourist submersible used to take people to see the wreck of the Titanic.

Mr Harding’s stepson Brian Szasz, said on Facebook: “Hamish Harding my step father has gone missing on submarine thoughts and prayers.

“My stepdad Hamish Harding has gone missing on a submarine pray for a successful recovery.

“Thoughts and prayers for my stepfather Hamish Harding as his Submarine has gone missing exploring Titanic. Search and rescue mission is underway.”

OceanGate Expeditions, a company that deploys submersibles for deep sea expeditions, confirmed that one of its submersibles had gone missing in the Atlantic Ocean and that a search is ongoing.

The company said in a statement that it was exploring options to bring the crew back safely and that it had received help from several government agencies in the process.

Action Aviation, an aviation sales and operations company which Mr Harding is chairman of, said on Twitter yesterday, that the billionaire was “currently diving” and was part of the Titanic expedition.

It is not clear how many people were on board at the time, but the submersible has a capacity of five people on board – a pilot and four guests.

The vessel operates by pinging back a message every 15 minutes to signal to those ashore that it is safe, however Sky News understands that those pings have not been heard from this vessel for more than seven hours.

The main difference between a submersible and a submarine, is that the former needs a mother ship that can launch it and recover it, while a submarine has enough power to leave port and come back to port under its own power.

The Titanic sank into the Atlantic on 15 April 1912 during its maiden voyage from Southampton to New York after hitting an iceberg, with some 1,500 people dying in the disaster.