Adrian Theobald is one of the few people in the world to have seen the inside of his own brain.
Adrian had a rare brain tumour
The 30-year-old insurance broker from south London was diagnosed with a brain tumour last year.
Adrian was told his only hope of beating the tumour was surgery.
Chemotherapy and radiotherapy would have no effect. Without surgery, he could be dead within five years.
However, it would be surgery with a difference. Henry Marsh, his neurosurgeon, wanted him to be conscious during the operation.
"I think the best way of operating on these tumours is by having you awake," he told Adrian, two weeks before the operation.
Mr Marsh, who is based at St George's Hospital in London, is one of just a handful of neurosurgeons in the world who do this type of operation.
He believes that it is safer for patients to be awake during some types of brain surgery.
"It sounds totally bizarre," he told Adrian. "But if you operate under general anaesthetic then people don't talk.
"You don't know whether that bit of the brain is terribly important for speech."
The operation was complex. The tumour was 6cm long and as with any brain surgery the risks were immense.
"It is extremely large," said Mr Marsh, speaking before the operation. "It is immediately next to the area of speech.
"There is a risk not just of damaging his ability to talk and to understand what is being said to him but also if things do go wrong, the results are catastrophic."
Adrian agreed to have surgery. "I'm going to have it done. I can't see any advantage of leaving it," he said.
Both Adrian and his wife Charlotte were acutely aware of the risks.
"I'm not really scared about the operation, I'm scared about the news afterwards," said Adrian.
"My fear is he won't be the same when he comes out," said Charlotte.
Adrian was anaesthetised before the operation started. Mr Marsh opened his skull and removed a sample of the tumour. Tests showed it was benign, boosting Adrian's chances of beating it.
A special mixture of drugs was then used to wake Adrian. He was asked to count from one to 10 and then back down again to show the surgical team he was OK.
Mr Marsh is one of the few surgeons to do this kind of operation
At the same time, Mr Marsh used an electrical pulse to find out where Adrian's tumour ended and where the region of the brain that controls speech began.
The pulse temporarily slured Adrian's speech, giving Mr Marsh a clear idea of what tissue he needed to remove.
Throughout the surgery, Adrian was asked to identify a series of pictures, such as a tripod, a compass and an accordion.
He could see his opened brain on a large television screen beside him.
"I feel fine, absolutely fine," he told the surgical team, halfway through the operation. "I want you to get as much out as you can."
Mr Marsh decided to stop the surgery after Adrian started to become muddled. He was no longer able to correctly identify some of the pictures he was shown.
He was anaesthetised again as Mr Marsh and his team closed up his brain.
The surgeon believes he was able to remove twice as much of the tumour from Adrian's brain by keeping him awake.
Over the course of four hours, the surgeon managed to remove 98% of the tumour.
Adrian slipped into a coma after the operation, giving Mr Marsh and Charlotte a scare. Luckily, he came around a day later.
"I was very worried something very serious has gone wrong," Mr Marsh said.
"I was operating on the verge of what most people would consider to be operable. It was very frightening to be honest."
Adrian talked to doctors during surgery
Eight weeks after the operation, Adrian says he's feeling fine. He will have to have regular brain scans to see if the tumour has returned.
"I'm pleased with how the operation went," he said. "Everyone seems to think it was a great success. Henry has prolonged my life without a doubt."
His wife, Charlotte is delighted with the results.
"He is still the same. His sense of humour is the same.
"We are thankful that we found it when we did and that Henry has done what he has done.
"We now just really hope that the future is rosy and that it doesn't come back."
"Fingers crossed," said Adrian and Charlotte together.
Adrian's story is featured on Your Life in their Hands on BBC1 on Monday at 2100GMT.