This is the story of Jamie McKechnie. Jamie was an upcoming BMX rider in South East London with a lot of promise. His friends described him as cocky at times but good at heart – and one hell of a rider on the BMX.

One night he was at the pub with his mates and they arranged a BMX holiday. They left the bar in a good mood, in the middle of summer, when they were confronted by an aggressive man shouting in a hoody and jacket, who after a brief altercation, walked on.

There was three of them at the time, one of whom later left to go home as they continued their walk on. They were walking towards the station when the man who confronted the group previously ran up from behind and punched Jamie in the back of the head – sending him forward onto the tarmac and knocking him out.

All photos: Channel 4 documentary 'One Killer Punch'

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Jamie suffered a severe brain injury from the incident. The documentary above was made as part of Channel 4 documentary ‘One Killer Punch’, which explores the dramatic repercussions of a single act of violence.

The man arrested for the crime was sentenced to three years in prison.

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It’s a heart-breaking watch at times. “The Jamie that existed before that punch doesn’t exist anymore," admits Jamie’s wife Ellen, who has been there with him throughout. But Jamie always wanted to get back on his bike.

Eventually, Jamie managed to do so. And the footage of him riding again – gaining “a sense of freedom" – is really amazing and showcases the power that the sport can have.

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We wish Jamie all the best with his riding!