On October 1, 2008, Mr Cairney got into a car driven by a drunk driver. They travelled along Auckland streets at 135kmh. Then, they hit a brick wall.
Mr Cairney is now 24 years old, and living in Wanaka.
The only outward signs of the trauma he suffered are the scars on his forehead, and a medic-alert bracelet.
Mr Cairney took the brunt of the impact. He lay in a coma for a month in the intensive care unit in Auckland Hospital. Once out of intensive care, he spent a further two months in hospital.
Mr Cairney has no memory of a year either side of the crash.
For Mr Cairney's mum, Penny Dever, memories of the accident are unforgettable.
"I was there every day at the hospital with him, most of the day.
"Initially, he wasn't going to live so we got through that first.''
Mr Cairney spent a year in a rehabilitation centre beginning the process of learning "everything'' again. Life is very different now.
He said former challenges such as sitting exams had been replaced by learning skills like how to brush his teeth. But he also has a new outlook on life.
'The new me'
Mr Cairney has a strikingly optimistic approach to what he calls "the new me'' but a knowing smile spreads across his face when he recalls who he was before the accident.
"Let's face it, I've come a long way.
"Even my haircut alone said it all - a mohawk over the top and a mullet at the back. You could just tell the sort of things I did.''
When asked for an example, Mr Cairney said before attending Kings College he had been "kicked out'' of Auckland Grammar after spraying an expletive into the carpet with an aerosol and setting it alight.
"It sounds crazy, but partially, I feel like this crash was almost a gift.
"Getting my head straight in an ironic way.''
This year, with the support of Graham Clarke and Giselle McLachlan, friends of Mr Cairney's mother, Mr Cairney moved to Wanaka to begin the next step in his recovery.
Ms McLachlan said she asked Mr Cairney if he would like to move to Wanaka after seeing how relaxed he was when he visited.
"George and I were out walking and he just really enjoyed the peace and beauty.
"I asked him 'what do you think about the idea of possibly coming to live down here, George?' and he immediately thought it was a great idea.''
She said the decision to support Mr Cairney to move had been about improving his health.
"We were watching a very unhealthy situation evolve for him and we felt strongly that the part of him that wasn't brain-damaged, that wasn't affected by the accident, needed a fair crack.
"And we were really sick of people telling George what he couldn't do.
"We wanted to focus on what he could do.''
Mr Clarke, a former organic farmer, said he realised "there might be a whole lot more George'' with the right environment and diet.
He said when Mr Cairney moved to Wanaka 11 months ago, his days had been structured around two or three naps, with minimal activity in between.
Now Mr Cairney regularly went to the gym, walked up Mt Iron, completed outdoor activities with Adventure Racer Simone Maier, and volunteered at a local cafe.
Mr Clarke said the change to Mr Cairney's condition had been "enormous.''
Both Mr Cairney and Mr Clarke said dietary changes, including cutting out all sugar, gluten and alcohol, had been a huge part of the improvement in Mr Cairney's condition.
"If nobody got drunk, none of this would happen'
Mr Clarke said alcohol was the cause of many tragedies, including his own. He said his son Mitch had been killed after drink-driving four and a-half years ago.
"My wee guy died as a drunk driver.
"He started off that night as a drunk, and the sober driver had taken everybody home, then some stuff went wrong and he was not equipped to make any decision at all, let alone an intelligent one.
"So off he went ...
"If nobody got drunk, none of this would happen.''
He said while he would have much preferred that he and Mr Cairney could have remained "ignorant of each other's existence'', it had been rewarding seeing the progress Mr Cairney had made.
"It has taken a very large combined effort of a family-type group to make things happen,'' he said.
Beanie Cafe owner Sue Irvine said Mr Cairney "comes and goes'' at the cafe. "He is teaching the staff a little bit about compassion and understanding.
"The staff appreciate his company and appreciate his struggles.''
Mr Cairney now lives with the assistance of carers, a group of women who Mr Clarke calls "superwomen''.
Ms Dever said she had not thought her son would be able to live separately from her.
"In my wildest dreams, I never imagined that he would be living independently of me and that he would be where he is right now.''
But life is not easy for Mr Cairney. The accident had shown him who his true friends were.
"I had hundreds of friends before the accident but only one or two of them have stuck around.''
Mr Clarke and Ms McLachlan were great role models, he said.
"I'm learning everything from them, from how to eat properly, to take magnesium, to not say awesome too often, because it is a feeling of awe which should be reserved for special things.''
Mr Cairney said his mother was a person who warranted use of the word.
"She is the best person in the world. She stayed at my bedside that whole time.''
Next year, Mr Cairney hopes to go on Outward Bound and speak to local high schools about the consequences of drink-driving.
"A benefit from all of this is hopefully my story can stop people from making the same mistake.''
