A BBC documentary contains the chilling moment when the Titan submersible implodes on its descent to 4000m below the ocean surface, to see the The Titanic. It is caught on a camera from support ship the Polar Prince, which was being manned by Wendy Rush, the wife of Titan’s pilot and OceanGate CEO Stockton Rush.

Wendy’s great, great grandparents - the former owners of Macy’s department store Isidor and Ida Straus - were two of the wealthy passengers who died aboard

The new footage, from June 2023, was obtained by the for its ongoing investigation into the disaster and shows Wendy hearing the sound of the implosion and wondering what it was. Initially she asks with a nervous smile: "What was that bang?"

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A moment later she receives a text message informing her that the Titan has “dropped two weights” which leads her to believe that all is well and the dive is proceeding as expected. But the text had taken a few moments to arrive, and had actually been sent before the implosion, which killed all five passengers instantly.

As they struggled to regain communication, those on board the Polar Prince did not notify the USCG for seven hours. When they did, it sparked a search which lasted four days until debris confirming the implosion was discovered.

Those who also perished, having each paid $250k for the trip, were British-Pakistani businessman Shahzada Dawood, 48, and his son, university student Suleman, 19, British businessman Hamish Harding, 58, and former French navy diver Paul-Henri Nargeolet, 77.

In the film experts line up to say how the was a disaster waiting to happen. Hinting at what is to come in the official report, due for release later this year, USCG Marine Board of Investigation Chair, Jason Neubauer, says: “Really, what we have here is not an accident, it’s a potential crime.”

Lieutenant Commander Katie Williams, from the USCG, believes the carbon fibre sub had been failing for around a year prior to the disaster, due to a process called "delamination". In that time, Titan took passengers on three more dives in the summer of 2022 - two to the Titanic and one to a nearby reef - before the implosion in June 2023. "Delamination at dive 80 was the beginning of the end," she says in the film. “And everyone that stepped onboard the Titan after dive 80 was risking their life.”

Discovery journalist and presenter Josh Gates was taken for a test dive and found the experience extraordinary - because nothing worked. “It didn’t do anything it was asked to do. It was non-functional,” he says. Stockton is shown in clips telling Josh that by the time the testing has finished, the sub will be “pretty much invulnerable” and joking that he uses “earplugs” to block out the sound of any cracking noises that might suggest problems.

“The red flag for me was like a flare had gone up,” Josh recalls. Deciding to ring his boss and pull his report, he explains: “I suddenly realised what would it mean if I made this promotional documentary about Stockton and about OceanGate that inspired other people to go and take a ride in this sub - and something happened to it.”

Karl Stanley, a fellow submersible pilot and deep sea exploration designer, has been on Titan and says he believes he narrowly escaped with his life, having heard many noises which seemed to suggest the hull was breaking under the pressure. “I’m sure we came within a few percentage points of implosion,” he says.

On OceanGate boss Stockton, Karl is scathing about the way in which he continued to take paying passengers on dives, regardless of safety. “He painted himself into a corner. If he admits defeat and failure, he then has to tell this to the people that had given him so much money. There is no possible way that Stockton didn’t know how this was going to end. It was obvious that it was going to fail in some way.”

He adds grimly: “People are spending a quarter of a million dollars on a death tube controlled by a game controller, that wasn’t tested, by a guy that’s telling you how he wants to be remembered for breaking rules. It’s a message to the super wealthy that their money can’t buy everything.”

Implosion : The Titanic Sub Disaster, Tuesday May 27 th BBC2, 9pm, and