Only six people in the world are known to have survived the so-called "hangman's injury".But Chris became the FIRST to recover fully after a risky seven-hour op to reattach his skull to his spine using titanium plates and screws.Mum Debbie, 43, said: "We didn't know if he'd even survive, walk or talk. So it's unbelievable he's back driving again."Chris was 12 when his car hit a barrier, trapping him, as he led the race in September 2006.Paramedics steadied his head - a one millimetre movement either way could have killed him - and took him to Southampton General Hospital.Doctors told Debbie and fiancé Paul Cornell, 50, that Chris had only a seven per cent chance of survival and the op was his only hope.Nine months later he was walking - after learning to speak and eat.And doctors cleared him to drive earlier this year.Debbie has outlawed car racing, but allows go-karting as it's "more controlled".Chris is now a regular at a track near his home in Fareham, Hants.Debbie, who has two other children with Paul - Patrick, 12, and Sophie, ten - said: "He's back doing something he loves, which is a miracle considering he was decapitated."Surgeon Evan Davies, who operated on Chris, said: "He's the only person in the world who has survived such an injury and gone on to lead a normal life. A few others survived, but they ended up completely paralysed."For Chris to make a recovery like this is truly remarkable."