Jason Black is just back from climbing the world's toughest mountain, K2. Bullied as a teenager, Jason also lost his mum aged 17. It was a very tough time in his life, but sport was his saviour. Since then, he has completed some of the world's toughest endurance challenges. But nothing quite compares to conquering K2. Here he shares his unbelievable story which is guaranteed to leave you with goosebumps.