Britain is ‘ready to provide assistance’ to the rescuers searching for Titan, the submarine which lost contact while on an exploratory visit to the Titanic, a spokesman for Rishi Sunak said this afternoon. The rescuers are facing a race against time as the craft runs out of oxygen. The expedition left for the site of the shipwreck – around 370 miles off the coast of Newfoundland – on Friday. The dive started on Sunday morning, and the submarine lost contact with the Polar Prince, the surface vessel, an hour and three-quarters after the descent started. It has been missing ever since.

British adventurer Hamish Harding is one of those thought to be on board, along with Pakistani businessman Shahzada Dawood, 48, and his son Suleman, 19, who are both British citizens too. The family is one of Pakistan’s richest. French explorer Paul-Henry Nargeolet and Stockton Rush – chief executive of OceanGate, the firm running the expedition – are both reported to be passengers too. Harding, 58, posted on his Facebook page on Saturday to say that the expedition was likely to be the only one running this year ‘due to the worst winter in Newfoundland in 40 years’. OceanGate charges guests $250,000 (£195, 270) to join one of its eight-day expeditions to the wreck, which lies 12,500 feet below the surface.

The operation is ‘like searching for a mine in a minefield’

The US coast guard has warned that the vessel probably only has around 40 hours of oxygen left in its emergency supply – but former submarine officer Frank Owen told the BBC that if the passengers start ‘panicking or moving around too much, they could exceed those rates’. He also said the operation is ‘like searching for a mine in a minefield’ because the submarine is probably among debris from the Titanic wreckage, and that, if it has sunk to the seabed, it is ‘well beyond’ the depth capabilities of most recovery systems. Mauger also told CNN that the search would be expanded into deeper waters. Marine scientist David Mearns has said that a commercial pipe-laying ship, which can reach depths of up to 3,800 metres, has just arrived in the area where the submarine was last located. He said there is ‘some hope’ that the ship could reach the submarine and help with its retrieval.

The US has sent two C-130 Hercules aircraft to look for signs of the vessel on the surface, while sonar buoys have been dropped to scan the water. US coast guard’s rear admiral John Mauger said this morning: ‘It is a challenge to conduct a search in that remote area, but we are deploying all available assets to make sure that we can locate the craft and rescue the people on board.’

In the case of a leak in the hull, ‘the prognosis is not good’, according to Alistair Greig, a professor of marine engineering at University College London. Professor Greig also said that if the submarine has gone down to the seabed – but is still intact ­– then if it is ‘deeper than more than 200m (656ft) there are very few vessels that can get that deep, and certainly not divers’. He added: ‘The vehicles designed for navy submarine rescue certainly can’t get down to anywhere near the depth of the Titanic.’

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