CAROLINE GRAHAM: The tears of the Titan tragedy relatives as they get back to dry land after their 'living nightmare'... as coastguard launches probe into deep-sea tragedy 

• Pakistani-British tycoon Shahzada Dawood, 48, and his son died on the Titan sub
• Flags on the sub’s mothership Polar Prince were at half-mast yesterday morning

The empty launch pad of the doomed Titan submersible was dragged away by investigators last night as grieving relatives and friends of the five dead men returned to land after their ‘living nightmare’.

Flags on the sub’s mothership Polar Prince were at half-mast as she sailed into St John’s, Newfoundland, yesterday morning, six days after launching the Titan on her disastrous 12,500 ft dive to the wreck of the Titanic.

British billionaire Hamish Harding, 58, the sub’s inventor Stockton Rush, 61, French pilot Paul-Henri Nargeolet, 77, Pakistani-British tycoon Shahzada Dawood, 48, and his 19-year-old son Suleman were ‘liquified’ when the sub imploded last Sunday – one hour and 45 minutes into its dive.

Bystanders wiped away tears at the sight of the empty launch pad being unloaded from the ship and taken away by Canadian coastguard officials.

A source said: ‘It was a very emotional homecoming. Everyone on board the ship is distraught. They have been going through a living nightmare. They have been trying to support the families on board, including the wives of two of the dead men.

‘They had to pack up personal possessions in the men’s cabins. There have been a lot of tears.’

Friends of Suleman, who attended Strathclyde University, yesterday released a touching portrait in tribute to the teenager, who family members said was ‘terrified’ of making the dive but did it as a Father’s Day gift.

His friend Isaac said: ‘During a very hard period of my life, when I was at my lowest point emotionally, he brought me back and made me feel positive about life again.’

Another mate, Joe, added: ‘There are a lot of people online assuming what he was because he was the son of a billionaire, but that assumption could not have been further from who Suleman was. He was the most helpful person I have ever met.’

The Royal Canadian Mounted Police last night announced an investigation. There are already probes under way by the Canadian and US Coast Guards.

The tragedy took place 435 miles south of St John’s in international waters in the North Atlantic.

The probe will focus on Titan’s experimental carbon-fibre hull and how Titan firm OceanGate bypassed classification and safety rules to carry tourists paying $250,000 (£195,000) each. More than 30 experts warned OceanGate’s chief executive Rush that the vehicle was a ‘death trap’ but he ignored critics and threatened to sue anyone who publicly criticised him.

Rob McCallum, a leading underwater expedition leader, released text messages in which Rush berated him for trying to sound the alarm, saying: ‘Stop saying I’m going to kill someone – I find it personally insulting.’

It is unclear who will head the investigation and whether any legal action will be taken to seek reimbursement from OceanGate for the millions of pounds spent on the rescue effort. ‘Expect a mountain of lawsuits, but they won’t bring anyone back,’ a source said.

Secret underwater US navy recording devices heard what sounded like an implosion last Sunday but a full-scale international rescue effort was launched because the US Coastguard demanded definitive proof the sub had imploded.

Pieces of wreckage were found on the seabed 1,600 ft from the bow of the Titanic on Thursday by a remotely operated vehicle.

It is unlikely that any human remains will be recovered, with McCallum saying: ‘At 12,500 ft, the water pressure is so intense, death would have been instant. It would have occurred before they knew what was happening.

‘They were liquified. There is nothing left to find.’

Some of those who have dived on Titan reported multiple systems failures including the communications system breaking down and the sub getting ‘lost’ in the ocean.

‘This was a death trap,’ said Don Walsh, a retired US navy captain, who was the first man to dive to the deepest part of the world’s oceans, the Mariana Trench, in 1960.

‘There needs to be a full investigation to ensure nothing like this ever happens again.’