TOP racehorse trainer John Quinn’s right hand man was a victim of Sudden Adult Death Syndrome when he died in his sleep, an inquest heard.

Sean McGuinness, 24, had been battling a hole-in-the-heart condition, which had ended his promising racing career in Ireland before he died in January, it was said.

His girlfriend Charlotte Buckle said Sean went to bed at 10.30pm at their home in Norton but never awoke.

She told the hearing at Scarborough: “Sean did not get up, which was unusual because he loved his job and would normally bound out of bed.”

She touched his face and it was cold, so she slapped him and when he still failed to respond she started CPR until the ambulance arrived.

A specialist examination by Prof Mary Stephenson in London showed Mr McGuinness had died from heart failure due to an irregularity in the beating of the heart.

There was no tissue damage and the heart was not an unusual size. Prof Stephenson agreed with other experts that death was due to Sudden Adult Death Syndrome, an unusual but well-recorded condition.

As a jockey, Sean had rode three or four winners in Ireland. But the hearing was told he was ordered to give up by the sport’s medical board after being diagnosed with a hole in the heart.

He had been appointed assistant racecourse trainer at Mr Quinn’s yard in Malton less than year before the tragedy in January.

Recording a finding of natural causes, Coroner Michael Oakley said it was clear the heart appeared normal but Mr McGuinness had suffered from an arrhythmia or some other condition, which would not show up after death.

Mr Quinn said in January that Mr McGuinness had the attitude and talent to go far. He said: “He was a great fella, a really decent lad with a great work ethic and a real team player.”