A Cambridge University graduate who died after holding his breath in an underwater challenge had been performing the same "party trick" since he was child, an inquest heard.
Dominic Hamlyn became unresponsive while swimming underwater lengths during his brother Benedict’s 21st birthday party at their family home in Crundale, Kent, in the early hours of July 28 last year.
The “fit and healthy” 24-year-old, who was an accomplished athlete, was taken to William Harvey Hospital in Ashford but he died around 15 hours later.
His father, neurosurgeon Peter Hamlyn, told the inquest in Maidstone he gave his son emergency treatment as Benedict held his hand while they waited for paramedics to arrive.
That night Dominic had challenged a family friend to swim lengths of the pool underwater and had swum about two-and-a-half before he was seen to be not moving.
Panicked friends pulled him out of the pool and a medical student at the party initially performed CPR before Mr Hamlyn took over until paramedics arrived at around 3.45am.
His father, an expert in sport-related injuries who saved the life of boxer Michael Watson after his near-fatal brain injury during his Chris Eubank fight in 1991, said his son had been unresponsive for “seconds rather than minutes” before being pulled out of the pool.
Mr Hamlyn had pushed for his son's death to be recognised as a result of 'sudden adult death syndrome' - something about which, he said, there was a great lack of medical awareness.
Peter Hamlyn said his eldest son could usually swim four or five lengths underwater – around double what he had swum on July 28 – and would take a series of deep breaths before doing so.
Experts had initially disagreed over the cause of Dominic's death.
“It was an entirely routine thing which I had seen him do since he was a child. It wasn’t unusual,” Mr Hamlyn told the court.
Assistant coroner Scott Matthewson gave Dominic’s cause of death as sudden adult death syndrome and said he died of natural causes.
Dominic, a graduate of University College London who had recently completed an MPhil in Business Studies at Cambridge, was described as “fit and healthy”.
He played cricket and rugby, ran the London Marathon in 2014 and had recently taken part in a university rowing race.
A post-mortem gave the cause of death as multiple organ failure with acute respiratory distress syndrome and drowning as contributing factors.
Pathologist Dr Olaf Biedrzycki, who had been asked to give an opinion, said it could have been shallow water blackout – a loss of consciousness underwater caused by a lack of oxygen to the brain.
But following a discussion with Mr Hamyln on Thursday morning, Dr Biedrzycki said that “on the balance of probability there probably was an underlying heart condition.
“If he wasn’t trying to do more than he had done before, that is slightly more likely than shallow water blackout.”
Professor Perry Elliott, a cardiologist instructed by the family, was also involved in the discussion with Dr Biedrzycki and gave a second opinion in a written report which favoured sudden death syndrome.
Mr Hamlyn and Dominic’s mother Geraldine held hands and wept as the assistant coroner gave his ruling, which acknowledged the differences in medical opinion.
“Nobody could have, or will ever with any certainty, say what the medical cause was in Dominic’s death,” Mr Matthewson told the coroner’s court.
He gave the cause of death as acute cardiac arrhythmia – sudden adult death syndrome.
The inquest heard that alcohol was not relevant and Dominic had given a speech at the party earlier in the evening.
