Ryan Darby was just 27 when he died from a heart attack in a hotel room in Bangkok.
To this day doctors still cannot tell his family exactly what happened on that September night in 2006.
He was one of eight apparently fit and healthy young people who die from undiagnosed heart conditions every week in the UK.
Ryan was engaged to Nicola Acuta or Cromwell Avenue, Bromley, when he died. The pair had a two-year-old son, Harley.
Since his death, Nicola has joined Ryan's family in supporting charity Cardiac Risk in the Young. (CRY).
Nicola says life without Ryan has been difficult but by raising cash for the charity she could be helping to stop another young life being taken away.
The 26-year-old said: "Ryan and I had long term plans for the future and you just don't think anything like that would happen.
"Unfortunately, it did.
"I spoke to Ryan on the Saturday before he died but then I did not hear from him again. He didn't meet up with his friends like he was supposed to.
"We didn't find out he had died until the Monday. It was just such a shock."
She added: "Having Harley has made things so much easier. I have Ryan's family living up the road, which is great, and my son is old enough to know he is helping to raise money for daddy's charity."
Nicola and the Darby family joined friends at CRY's Heart of London Walk on July 20. This is an 8km trek which crosses eight bridges in the capital.
Family and friends also raised £9,000 at a fundraising evening in July last year.
Ryan's retired dad, John, said: "It is the worst thing in your life to lose an only child the way I lost my boy.
"People don't think it will ever happen to them but it does.
"If we can just stop this happening to one other young person the fundraising will all be worth it."
Surrey-based CRY puts cash into screening programmes and medical research to help raise awareness of conditions which can lead to sudden and unexplained cardiac death in apparently fit and healthy under-35s.
It is currently campaigning to introduce routine screening for teenagers in secondary schools.
'PUBLIC SUPPORT HUGELY IMPORTANT'
Charity Cardiac Risk in the Young (CRY) was set up in 1995.
It aims to raise awareness of undiagnosed heart conditions, including sudden cardiac death and sudden arrhythmic death syndrome.
Sudden cardiac death is brought on by exercise.
In 10 per cent of sudden cardiac death cases, no recognised cause of death can be found – even after a post-mortem examination.
The diagnosis then changes to sudden arrhythmic death syndrome.
Alison Cox, MBE, CRY's chief executive and founder, said: "Public support for our fundraising event is hugely important to progress our key services, such as life saving cardiac screening."
