The swanky surroundings of The Witchery are the last place you'd expect to see Guy Grieve. And yet, when I tell the restaurant's impeccably-dressed maitre d' who I'm here to meet, he responds with an arched eyebrow and: "Oh yes, our devastatingly handsome scallop diver."
• Guy Grieve with his catch on the Royal Mile Picture: Dan Philips
At this point, Grieve, 36, makes an appearance - and yes, he is Action Man made real. Tall and rugged, he wears jeans and a white T-shirt and looks like he's stepped, slo-mo, straight out of a Diet Coke advert.
Today's casual get-up is very different to what he might have been sporting a few years, when he spent his days chained to a desk in a 9-5 marketing job which he hated. In the six years since he ditched the suit however, his life has followed an extraordinary path which has led him here, to The Witchery, one of a number of Scottish restaurants - a list also including Prestonfield House, Ondine, The Kitchin and Andrew Fairlie at Gleneagles - which he supplies with scallops and other seafood through his fledgling business The Ethical Shellfish Company.
In 2004, Grieve had long since passed boredom, achieving a sort of semi-coma state as he spent three hours a day commuting to his desk job. For someone who describes the outdoors as his "church" this was hell. He had reached breaking point when he decided he had had enough. Drastic action was required - and the action he settled on was more drastic than anyone could have imagined.
He left behind his wife Juliet and their two young sons, Luke and Oscar, to spend a year alone in the wilderness of Alaska. Upon his return, Juliet had sold the family home in the Borders and moved with the children to Mull, where her parents live. Far from having given up on her misty-eyed husband and his itchy feet however, her motivation had been ensuring that upon Guy's return he didn't fall back into a lifestyle he had come to hate.
The Alaska adventure gave him the motivation he needed to change his life for good, but he brought the whole family along on his next journey - a year-long sailing trip round the world in 2008, during which the foursome encountered everything from pirates to chronic seasickness.
Today his adventures take place a little closer to home, but 30 metres under the sea. "After I stepped off that boat I thought a lot about what I should do next," he says, with a boundless enthusiasm which, it becomes clear, is never-ending. "I also needed to put beans on the table. I was thinking about all sorts of stuff to do with wild places around the world, then I suddenly realised that I'm surrounded by this immense, incredible wilderness called the North Atlantic. Not only is there going to be great adventure here, but I can just continue this link that we made with the sea."
With the support of Juliet, Grieve set up The Ethical Shellfish Company last year. The couple re-mortgaged their home and maxed out three credit cards to set up a business which, as the name suggests, has ethics at its heart. He now supplies British seafood to British restaurants. Fish are line-caught and scallops are hand-dived, many of them collected by Grieve himself, who sticks to a gruelling schedule of early rises and three to four dives a day.
He does not buy from trawlers or dredgers; he talks repeatedly about being motivated by respect for the seabed, not greed. He does not wish to rile his fellow fisherman, but he is appalled at the way in which this hidden wilderness is being pillaged through intensive fishing.
After getting his diving licence, it didn't take long for him to see first hand the devastating impact that the fishing industry has had on the sea bed. As he grew familiar with the underwater terrain, he began to notice when things weren't as they should be.
"There's one place I dive where I drop down to about 25m and I land in this garden of tremendous biomass and habitat," he says gravely. "Every nook and cranny is full of life. Lobsters, crabs, scallops, every kind of life imaginable.
"And then I just come to a line where the secret garden ends and the result of man's rampaging begins. There is nothing. It is gone. The sea bed has been ploughed. Where once there would have been endless habitat you just see nothing; smashed shells, giant rake marks in the ground. Like a ploughed field."
To say that he talks passionately would be a gross understatement. He is consumed with the damage we are doing to this unseen wilderness, and frustrated at the lack of attention it gets. One television executive he approached to try to get some coverage of the issue told him that "the sea bed simply isn't sexy".
Other people have called him nave - certainly he has the sort of optimism you wish you could bottle and sell.
But I find myself wondering if he'll stick at it or if he'll hanker after bigger adventures. Is this simply the latest in a string of self-improvement projects? Come next year will he be craving the next adventure?
"No," he says firmly. "I've wandered about quite a bit and for the first time in my life I've discovered a real sense of purpose. It's all come together so unexpectedly that I feel this is what I've got to do.
"This is how I can support my family, this is how I can contribute to the safeguarding and protection of the sea bed. The outdoors is my church, it's where I want to be. When I was working in an office it had no meaning, whereas this really has got such a lot of meaning. When I got back from Alaska everyone would ask me, 'Why did you do it?' And invariably I'd tell them that I don't know yet, but if you come back and speak to me when I'm 60 I bet you I'll be able to give you an answer.
"Now, when I look back on it, I realise just how much Alaska is with me every day that I'm fishing because it was my first wilderness and it was the first time I was in a place where you had to give way to nature, not the other way around. It was boss. And it buried deep in my heart a majorly profound love for wild places."
It may not be the bleak white terrain of Alaska in the depths of winter, nor is it the pirate-strewn waves surrounding South America, but in the waters off Mull, Grieve has found his own private wilderness, achieving a contentment in the process and sating his wanderlust. He may not have known at the time just what drew him to Alaska, but by going from the 9-5 to the extremes of the sub-Arctic he has been able to find a happy medium between the two in the form of The Ethical Shellfish Company.
"The whole experience of being in a wild place is very familiar to me," he says. "Spiritually it's been one of the most enriching jobs I've ever had and that's because whenever you're in a true wilderness, you are confronted with your mortality. Every time I drop off that boat, four times a day, I have to consider in vivid terms my life, whether I'm going to live or die. It's quite an experience.
"And when I reach the seabed and gradually accustom my eyes to the dark, every day this new wilderness just starts to kind of appear. That's really thrilling. And then I know I've got 20 minutes here. If I stay any longer I'm dead. So each time I break the surface again it's like being re-born.
"I long to be back on a boat on the high seas again, but I've realised that the time for that is over now and I love being in the Scottish islands and this is where I'm going to find my wilderness. I've found it. But I've got to stick up for it. "
Guy Grieve's Alaskan Adventure
It ALL started for Guy Grieve in Alaska in 2004, where he had broken free from his well-paid corporate job (ceremoniously burning his suit) to live out his dream in the wilderness.
He came face-to-face with grizzly bears, fell through thin ice and went months without seeing another human being. Some 60 miles from the nearest outpost, he pitched his tent and set about building a log cabin, felling the trees around him to make his home for the next 12 months.
The natives told him that he was too late, that he had begun building too close to the winter to be finished on time. In fact, the only thing he had constructed before his trip was a cabinet from Ikea, but he managed to make his home using traditional local building techniques.
He lived on beaver meat and kept a dog, Fuzzy, as a companion, as well as a pack of huskies for getting around. He wrote and read to pass the time, all the while worrying that he might just lose his mind.
But he survived, knowing that on his return he would "hug his children for a week" and never again put on a tie.