A 24-year-old Cambridge graduate died after suffering a cardiac arrest while taking part in an underwater swimming challenge with a friend, an inquest heard.

Dominic Hamlyn suddenly stopped moving in the pool at his family home in Crundale, near Canterbury, in the early hours of July 28 during a family party.

His devastated mother "screamed and screamed" after being told doctors were unable to save her son, who was the oldest of three “extraordinary” brothers.

The strong swimmer had challenged a friend to see how many lengths they could do underwater, the inquest in Maidstone heard today.

Dominic, who was described as gifted both academically and in sport, was known to be able to manage five lengths beneath the surface but stopped after just two.

Tomas Ter Reehorst - a pal of Dominic's brother Benedict - had swum one-and-a-half lengths underwater before giving up and going over to his girlfriend at the side of the pool.

They shared a joke and, seconds later, Tomas’ girlfriend went to challenge Dominic to another swimming challenge but found Dominic motionless in the water.

They pulled him out of the pool and started CPR immediately and an ambulance was called at 3.24am.

In a statement, his dad Peter Hamlyn described the moment his son's 'hysterical' friends came to find him.

"I assumed calm, old dad will find nothing much to worry about.

“I hurried there and quickly realised it was serious and took over resuscitation.

"He showed no signs of life at any point.

“I turned him over and tried to get the water out of his lungs but was unsuccessful.”

He desperately gave his son CPR while Benedict held his brother's hand, but Peter says Dominic didn’t ever respond.

Paramedics arrived after seven minutes and found a weak pulse before taking him to the William Harvey Hospital where he was treated throughout the day.

Dominic was not stable enough to be taken to King's College Hospital in London so a team came to Ashford to help deliver treatment.

But his condition never improved and he suffered a brain haemorrhage at about 5.30pm.

Peter, a world-famous neurosurgeon, said: "I told Geraldine it was hopeless and she screamed and screamed and screamed."

Dominic died at 7.24pm.

The former Kings School pupil, described by his father as a "superb athlete", had been celebrating his younger brother Benedict's 21st birthday at the house.

The party, attended by about 40 guests, was a "well behaved and polite" event. Dominic made a speech and hadn't drunk before this, only afterwards.

He was about one-and-a-half times over the drink-drive limit - but the alcohol did not play a part in his death and irrelevant, the inquest heard.

Before taking part in the underwater swimming challenge, both Dominic and Tomas did a breathing exercise to help them stay beneath the surface for longer.

His father Peter told the inquest Dominic had done this frequently since a child.

"They would stand at the shallow end of the pool and take some deep breaths then nod at each other when they’d had enough and set off,” he said.

Pathologist Dr Olaf Biedrzycki, a witness at the hearing, spoke about two possibilities which had caused his death; an underlying cardiac problem or shallow water blackout.

The latter is caused by lack of oxygen to the brain caused by holding your breath for too long.

But Dr Biedrzycki says Dominic had carried out the breathing exercises many times before and so wasn't doing anything out of the ordinary.

“He'd done it since he was 11,” he added.

"On the balance of probability, there probably was an underlying cardiac problem."

Dominic's family believe he died as a result of Sudden Athlete Death Syndrome - and that tragedy could have struck at any time.

And concluding, assistant coroner Scott Matthewson, said it was a “primary cardiac event”.

He said: "Dominic died after suffering a cardiac arrest as a result of an undiagnosed disorder while swimming.”

He recorded the death as from natural causes.

Dominic's death in July sparked an outpouring of tributes from those who knew him.

Peter Roberts, headmaster of The King’s School, described him as a “talented and charming young man”.

Mr Roberts added: “He shone in the classroom, on the sports pitch and in every social context by the brightness of his mind and his charismatic personality.

“Our hearts and support go out to his parents, brothers and family.”

Dominic went on to study at UCL in London, from which he graduated with a first class degree in science and engineering in 2017. The accomplished scholar then studied for a Master of Philosophy at Cambridge University’s prestigious Judge Business School.

Outside of his studies, he was a long-standing member of Selling Cavaliers Cricket Club.

Secretary Roger Wynde said: “Dom brought an energy and spirit to everything he did, including his cricket.

“He was such a talented sportsman and was hugely popular with everyone at our club and beyond.

“He will be greatly missed by all who knew him.

“All our thoughts are with his family and friends at this very sad time.”

In 2014, he ran the London Marathon in aid of The Brain & Spine Foundation - for which he managed to raise almost £5,700.

On his fundraising page, he said he was inspired by the number of people in Crundale who have been affected by neurological and spinal conditions, as well as the death of his baby cousin, Maria.

He was also motivated after seeing his father and his patient Michael Watson - a former boxing champion - walk the route together.

Dominic wrote: “It took them six days and I swore when I was old enough I would run it; in the words of Michael, ‘for the benefit of others less fortunate than me’.”

Mr Watson, whose life was saved by Dominic’s father in 1991, said: “I loved him and knew him since he was a little boy.

“I was so touched that he was inspired to run the London Marathon because of me and help improve the lives of others’.”

In a statement released after Dominic's death, Mr Hamlyn said: “Why did he die? He was a superb athlete competing in both rugby and rowing at Cambridge.

“We are broken. If Dominic is to be remembered it is as a hero and one of the world’s helpers.”

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