ED Stafford went into the Peruvian jungle in April 2008.
Eight hundred and sixty days later he came out on the other side of South America having become the first person to achieve the "impossible" by walking the length of the Amazon.
It was an endeavour described by Sir Ranulph Fiennes as "truly extraordinary" and "in the top league of expeditions past and present".
Over the course of 6000 miles Stafford faced starvation, was bitten by scorpions and mosquitoes, accused of murder and threatened and imprisoned by machete-wielding tribesmen.
And as if that wasn't enough, the man who started the journey by his side quit and then, as the global recession kicked in, his sponsors withdrew funding. There was only one thing to do. Keep calm and carry on. So he did.
He filmed himself and kept a blog of his experiences.
This became Walking The Amazon, the best-selling book now translated into eight different languages, and a TV series on the Discovery Channel
There was to be no going back to leading expeditions for corporate clients (to be paid peanuts) while security work in Afghanistan just would not cut the mustard any more.
Instead, there were lucrative motivational talks and offers of what he describes as "rubbishy TV".
"You know, You are a Walking Man and you are going to walk across here, there and everywhere."
But Stafford wanted to do something else. It turns out he wanted to try and survive on an uninhabited island in the middle of the Pacific Ocean for 60 days with nothing other than a camera for company — not even clothes.
"I'd already done 860 days in the Amazon," says the 37-year-old. "I mean, how hard could it be?"
THIS IS HIS STORY
After what seemed like an age getting to the island of Olorua, my producer finally said, "Right Ed, here we are, take your shorts off".
I was like, "Really, are we actually going to do this?"
The idea had always been there on paper but this was actually it so I jumped out of the boat, naked, with these Fijian boatmen looking at me as if I was insane.
Feeling stupid as much as daunted, there I was.
Alone. On an island. Miles from anywhere — and naked.
I immediately had to ask myself what the hell I thought I was doing
Originally I was going to be on the island for 40 days but David Blaine had done that in a stupid glass box with no food so we decided on 60 days as it had to be a length of time that showed you'd cracked it and if you hadn't mastered the environment you would have died.
The nearest civilisation was a remote island — eight nautical miles away — where a Fijian clan, the Komo, live and an emergency boat was located. Within the first hour I had a major panic attack.
It was a disturbing feeling not immediately eased by the fact that the water source — alongside its remoteness, a key reason for choosing the island in the first place — was actually little more than a wet rock.
When the production team had visited the island there had been heavy rainfall and so there was a trickle but that wasn't the case when I got there so I had to rig up a contraption that drew the water away from the rock and it provided for one drop every 40 seconds.
That was my water source so it was coconuts until it rained. Not a great start.
I wasn't sure about having "Naked" in the title (of the show) because it makes it sound like a stunt. But it does make people stop and think: "Wow, he actually has nothing, not even a knife."
It was something I was thinking about as I nibbled away at the bark of a tree with a giant clam shell for 11 days just to build a shelter. It might have been bomb-proof and waterproof in the end and it's probably still standing but if I'd had a machete, just that one tool, I would have been able to build it in a few hours.
The amount of energy everything took was massively beyond what I expected. And it was mentally taxing.
The weird thing is that if you lose all your kit and are in survival mode on a normal expedition you hope it will only last a couple of days.
In this case, not only has everything been taken away, you're actually allowing yourself to be in a survival situation for that amount of time.
It's concentrated and you're on your own. Even in the Stone Age people would have been born into a shelter with furs and firewood and, during childhood, picked up the skills needed to survive.
It was two weeks before I managed to light a fire — you'll be able to tell how happy that made me when you see the show.
There were eight feral goats on the island, four adults and four kids. I saw them on day one and they seemed to taunt me by coming so close I could almost touch them.
I made a bow and arrow.
In films, the arrow leaves the bow at high velocity and brings down an animal in full flight but this just went twang and fell on the floor.
And my spear wasn't sharp enough.
So, when the hunting tools didn't work, I spent seven days building a coral-type trap with spikes on it and everything.
I thought "Yes. This'll do it". It didn't.
On about day 43 I was walking round the island looking for crabs and saw what I thought was driftwood caught up in the bottom of this tree.
Then it bleated.
This goat had been eating the leaves, got its horns caught and panicked. It was a massive thing, about 45 or 50 kilos and it was meat, so I tried squeezing its windpipe but that wouldn't do it and then I had to bash it on the head with a clam shell.
It took about 15 minutes to kill it and was quite gruesome. It showed me how far I was from being able to hunt because even though it was trapped it still took me quarter of an hour.
It was a massive morale-booster though. I killed the goat at about 11 o'clock in the morning and by the time it got dark I'd got the whole thing completely skinned. I cooked up the heart, the kidneys and the liver. I hadn't eaten all day so that was amazing and then the next morning I had a huge rack of ribs.
I dipped the steak meat in sea water for the salt and hung it over the fire so it turned into quite crisp jerky. It took eight days to eat the whole thing before it was back to the depressing business of eating snails again.
The physical side was tough but ultimately fine. I did a series of exercises on the beach every day — press-ups, chin-ups on a tree branch, squats with boulders on my shoulders and shuttle runs of about 300 metres that I timed on the camera.
At the end of week eight or nine I had managed to get to a stage when I was getting stronger. The difficulty was elsewhere.
In the army it's called the "top two inches" — that is to say, the mind. That was absolutely the case on the island.
I hadn't seen the film Castaway before I went but I knew what it was about and how the main character, Tom Hanks, finds a volleyball washed-up and names it Wilson (after the brand).
He gives the ball a personality and develops a relationship with it which sounds crazy but I watched the film after I got back and I can tell you that it was remarkably well done and pretty damn accurate — I could totally relate to it and the mental deterioration you can experience if you don't fight to keep control.
In the past there had always been someone to unleash the frustration upon but there wasn't on this occasion and so it was internalised and needed managing.
I'd guessed before the trip that being by myself was going to cause extra problems but I didn't realise to what extent and probably didn't pay it enough attention.
The waves of panic that would come over me when there was absolutely no-one to turn to was astounding, a complete and utter sense of self-reliance and responsibility for yourself is a weird place.
The one thing that helped me was that I had been to Australia and spent a week with a couple of Aboriginal guys. They explained about their walkabout (coming-of-age) ceremonies, about being dropped out in the bush with absolutely nothing and just having to cope.
The best trick they taught me was to make a circle of stones and to retreat within it whenever the panic kicked in. It was almost a kind of meditation and while I'm not a spiritual guru or anything like that, it worked for me.
The other thing that helped was the camera. It may sound weird but it felt like I was sharing the experience, like when I started a fire. It was also an excuse to speak out loud.
Usually if you're on a desert island and you start talking to yourself it is an indication that things are going wrong - and that's not to say the cameras didn't catch me singing to myself or having a little dance. I suppose the camera was my 'Wilson' to some degree.
I'm back home now and 13st 11lb, almost back to my fighting weight of 14 and a half stone. I'm in good physical shape but it took me a few weeks to recover mentally from the experience.
As I've said, I didn't really pay enough attention to how the isolation would have an effect. I've learned a lot and picked up new skills.
At the moment I'm loving life, planning my next adventure and in talks about what it might be.
All I can say at this stage is that it will incorporate a range of experiences.
No change there then.