A GRIEVING father whose fit and active 12-year-old son died moments after winning a school swimming race last night vowed: “I won’t let my Ollie’s death be in vain”.

An unknown underlying heart condition took Oliver King’s life during a sports lesson at King David High School, in Childwall, in March last year.

Now his family are hoping to set up screenings for thousands of Liverpool children and install life-saving defibrillators.

The youngster, a talented footballer who trialled with Everton and Liverpool, was seemingly the healthiest child in his class.

He had the quickest fitness “bleep” test (a shuttle run) time for his age on Merseyside – and even jogged when walking the family dog.

Oliver had no time for computer games and TV.

His fitness was such that his father, Mark, did not look twice at leaflets given out when his son’s Woolton Diamonds football team – which he manages – were playing at Camp Hill pitches six months prior to the March tragedy.

The leaflets told of a condition called Sudden Arrhythmic Death Syndrome (Sads), a silent killer which claims the lives of 12 young people a week, 634 a year.

Oliver King was one of those victims.

Mark, 49, said: “I didn’t know anything about it or what it was.

“I remember people from Cry (the charity Cardiac Risk in the Young) were handing out leaflets explaining it all.

“But at the time I brushed it off. Oliver was really fit, I thought it would never happen to him.

“He had never been ill. He was as fit as a fiddle, probably the fittest kid in his school.

“There were no warning signs. He went to school that day and he should have come home.

“He didn’t and we miss him so much.”