The mother of the teenager who died in the Titan sub disaster with his multi-millionaire father has revealed she was originally due to be on the doomed vessel but gave her place to her 19-year-old child because he 'really wanted to go'.

Christine Dawood and her husband Shahzada Dawood had initially booked a trip to the Titanic wreck for themselves but had to cancel due to the pandemic.

She said that when their family reserved spots on this year's OceanGate Expeditions mission, she 'stepped back' because her son Suleman, 19, was so keen to go.

The family boarded the Polar Prince, the sub's support vessel, on Father's Day hoping for the trip of a lifetime. Mrs. Dawood and her daughter Alina, 17, were still on board when word came through on June 18 that communications with Titan had been lost.

She and her daughter held out hope after they did not initially return but admitted she 'lost hope' when 96 hours had passed since her husband and son boarded the submersible, which indicated they had run out of oxygen.

The grieving mother said her daughter held out a bit longer until a call with the US Coast Guard last Thursday when they were informed debris had been found. It then became clear that an implosion had taken place.

The US Navy had detected sounds 'consistent with an implosion' soon after Titan lost contact on Sunday, but it was deemed 'not definitive' and the detail was not released publicly - with the search and rescue mission continuing until debris was found.

Speaking about initially holding out hope, Mrs Dawood told the BBC: 'We all thought they are just going to come up, so that shock was delayed by about ten hours or so.

'By the time they were supposed to be up again, there was a time.... when they were supposed to be up on the surface again and when that time passed, the real shock, not shock but the worry and the not-so-good feelings, started.

'We had loads of hope, I think that was the only thing that got us through it because we were hoping and... there were so many actions the people on this sub can do in order to surface... they would drop the weights, then the ascent would be slower, we were constantly looking at the surface. There was that hope.

'There was so many things we would go through where we would think "it's just slow right now, it's slow right now". But there was a lot of hope.'

She said she 'lost hope' when 96 hours had passed since her husband and son boarded the submersible.

She revealed that is when she sent a message to her family saying she was 'preparing for the worst'.

UK-based businessman Shahzada and Suleman were two of the five victims killed instantly when the submersible suffered a 'catastrophic implosion' just 1,600ft from the bow of the Titanic, according to the US Coast Guard.

Mrs. Dawood revealed that she had planned to go with her husband to view the Titanic wreck in the OceanGate sub, but that their trip was cancelled due to the Covid pandemic.

'Then I stepped back and gave them space to set [Suleman] up, because he really wanted to go,' she said.

'I was really happy for them because both of them, they really wanted to do that for a very long time.'

Mrs. Dawood shared how she and Alina hugged and joked with Shahzada and Suleman before the pair entered the submersible.

Suleman, a student at Strathclyde University, had taken his Rubik's Cube on the trip as he hoped to break the world record for solving the puzzle at the greatest depth, she revealed.

'He said: "I'm going to solve the Rubik's Cube 3,700 meters below sea [level] at the Titanic,"' Mrs Dawood recalled.

Her son, she said, was practical and intellectual, and wouldn't go anywhere without his Rubik's Cube, which he taught himself to solve in just 12 seconds.

'Suleman did a 10,000-piece lego Titanic. He applied for a world record because he wanted to solve a Rubik's Cube at the deepest point.'

While his application was rejected, they were still planning to film the attempt.

Mrs. Dawood said she and her daughter have vowed to try to learn to finish the Rubik's Cube in Suleman's honour, and she intends to continue her husband's work.

She said: 'He was involved in so many things, he helped so many people and I think Alina and I really want to continue that legacy and give him that platform when his work has continued and it's quite important for my daughter as well.

'Alina and I said we are going learn how to solve the Rubik's Cube. That's going to be a challenge for us because we are really bad at it but we are going to learn it.'

And the heartbroken mother said through tears: 'I miss them. I really, really miss them.'

As well as her husband and son, three others died on board Titan: OceanGate's CEO Stockton Rush, 61, British businessman Hamish Harding, 58, and Paul-Henry Nargeolet, 77, a former French navy diver and experienced Titanic diver.