By Jamie Roberton and Natalia Jorquera
Steve Mallen can still vividly recall the Monday afternoon when two police officers knocked on his front door and told him that his son Edward had killed himself.
"It was like someone had opened the front door and thrown a hand grenade in the house, maiming everyone inside irrevocably," he says.
Tipped by his peers as the most likely to become prime minister, Edward was a gifted and popular A* student about to accept a place at Cambridge University.
But over the course of eight weeks, the 18-year-old descended into a deep depression and - following a catalogue of errors by local mental health services - took his own life on railway tracks near his home.
As he stood beside his son's coffin, Steve made Edward a promise: he would investigate the tragedy of his death and fight for reform to stop others in his generation meeting the same fate.
"We are losing some of our best and our brightest; the future of the country is being lost which can so easily be changed."
Fuelled by the belief that Edward's death could easily have been prevented, Steve embraced the "Zero Suicide" initiative, a concept which first emerged from a Detroit hospital more than a decade ago.
The aim is simple: a better-coordinated, more proactive strategy which intervenes earlier - rather than reacting once patients have reached crisis point - will save substantially more lives.
The aspiration is to eradicate suicide or at least radically reduce the estimated 6,000 deaths that occur every year.
"Zero is an aspiration. If zero isn't the right number what is? We have to move in that direction.
"I want to stop people from feeling suicidal in the first place and in order to achieve that we need to go back into communities and look at what's happening in families, the school system to make sure we are producing more emotionally intelligent and resilient people but also a system that is able to detect difficulty much earlier than it is.
"My dear son was very, very desperately ill by the time he sought professional help and it could so easily have been averted."
Steve's uncompromising desire to bring about genuine and meaningful change is striking as I speak to him on a cold Monday morning in King's Cross.
The 52-year-old is in no doubt that his extensive corporate experience can help implement the system-wide reform he believes this country's young people so desperately need.
But as Steve openly admits: he is "just a sad father trying to honour his boy".
"He was academically brilliant, he was a gifted concert pianist, he was our oldest child, the first grandchild in the family, he played for the local cricket team, he delivered newspapers in our village, he was head boy in both his primary and secondary school.
"To be perfectly honest with you, he was most fathers' idea of a perfect child."
It was not just Edward's academic and musical talents that set him apart, according to his father - it was the deep sense of care he had for his friends and family.
It was this quality that made Edward - "ironically" his father says - the go-to person for his friends when they wanted to talk about their own troubles.
But unbeknown to those closest to him, Edward was being increasingly consumed by his illness.
He told numerous medical professionals that he was considering jumping in front of a train; he even gave consent for his parents to be told of the severity of his thoughts.
They never received a call.
On 9 February 2015, Edward was found dead at the station where he caught the train to school every morning.
"We had no idea about how poorly he was - he went from being one of the brightest prospects of our generation to absolute catastrophe in a matter of weeks," Steve says.
Edward's sudden death had a seismic impact on the close-knit community in Meldreth, Cambridgeshire, with more than 500 people attending his funeral.
In a moving tribute, friends arranged for one of his piano performances to play over the church soundsystem.
"As a father, there are no words to describe hearing your own son playing as his coffin is taken into the church."
Two years on, Steve is adamant that while the stigma around mental health is being destroyed, only minimal improvement to frontline services has been achieved with patients still facing a "postcode lottery".
"You can't pick up a newspaper now or turn on the television or radio without hearing about mental health. We have celebrities talking about it, we have sportsmen, we have the Royal family - it is one of the burning social issues of our time.
"But make no mistake, right now in this country there are tens of thousands of young people who are waiting months for therapy they so desperately require."
Asked whether his Zero Suicide project will require a huge funding injection from an already cash-strapped government, Steve shakes his head.
"That cash doesn't exist so therefore we have to work within the art of the possible."
He wants to ensure there is a joined-up approach where the best practices from all mental health trusts are shared and implemented; while everyone in communities - from dinner ladies to parents - are trained to identify the signs of mental illness.
He also passionately believes that children should be taught about the causes and nature of depression in the classroom.
"It's much more about what can we do with the system we have to re-engineer, integrate and improve standards?
"If we can intervene and treat people more quickly and more radically, then we can stop them reaching crisis and if we stop them reaching crisis, we can obviously bring down the suicide rate."
So when will he know that he has reached his goal?
"When I can feel comfortable that were my son to walk into hospital with the same presentation that he did, that he would still be sitting her with us and, at the moment, we are a very long way off from me being able to say that.
"I'm not sure if my son walked into a hospital today that the outcome will be any different than it was two years ago."
Steve tireless work is showing no sign of slowing; after our interview, he is rushing to the Department of Education to discuss his campaign.
I ask him whether he believes Edward would be proud of his efforts.
"I can only hope so," he says, his voice faltering for the first time. "I was certainly proud of him."
If you are in distress or need some support, the Samaritans are available 24 hours a day on 116 123 or through their website