The cousin and goddaughter of Hamish Harding has called for a full investigation into the deaths of the five Titan passengers.
In an interview with BBC special correspondent Lucy Manning, Lucy Cosnett asked what safety checks had been in place before the tragedy.
“It should be fully investigated, to see what went wrong, why it happened, why they didn’t survive,” Cosnett said.
“He [Harding] was going to have his birthday tomorrow. He’d be 59 years old. I would have sent him a message or tried to call him to wish him happy birthday.”
Reflecting on the last few days, Cosnett said: “When I read they had heard banging noises I was feeling hopeful that maybe it was coming from the submersible.
“But then yesterday was the worst when I heard that he didn’t make it, that they all died,” she said.
Meanwhile, the experts say any investigation into the Titan sub will undoubtedly focus on trying to work out what exactly happened to it – but how will experts do this?
One of the things they will be looking to do is examine the debris.
In particular, they will be looking for the site of the rupture – which will be hard because the Titan’s body is in small pieces, and harder still because it is being collected by remotely operated vehicles (ROVs) in the darkness of the deep sea.
Another focus of the investigation will be whether there were sufficient checks following each dive. Each time the Titan went down on a deep dive, its hull would have been compressed by the immense water pressure – it would have become smaller and then returned to its normal size on its return to the surface.
This regular stress would have led to fatigue of the material, weakening it. It is so far unclear whether there were checks for cracks after each dive and if so how extensive they were.