Today, David, 25, is a successful, eloquent civil servant. A private secretary in a government department, he holds a law degree and a masters in legal and political theory from University College London.
His friend Stephen Lansana, meanwhile, is serving life for murder at HMP Whitemoor, a Category A prison in Cambridgeshire. He will be in his 50s before he will be even considered for release.
As teenagers, they were no different, except in one very important respect — the opportunities afforded to them.David, you see, was given a scholarship to Rugby. So, is that the answer?
This week, London Mayor Sadiq Khan announced plans for a Violence Reduction Unit. Violent crime, he said, should be treated as a public health problem — a 'disease infecting communities' — requiring action to tackle the root causes.But what are those 'root causes'? Is it simply lack of money? What does David say he noticed most at Rugby?
"But most poignant to me was the presence of both parents actively taking an interest in the education of their children."
David is still involved with EYLA, mentoring youngsters.
'I'm not sure what the long-term solution is, but what I see in my community is lack of aspiration and a here-and-now mentality.
'Young people tend to make their decisions in view of the short-term, quick gain, easy routes,' he says.Since we can't retrospectively travel back in time and somehow ensure two parents stay together to raise a child, what can Khan do?
It's way too late to tackle the Loxodonta africana in the room...