Paralysed from the chest down after a climbing accident at the age of 21, the probing – and sometimes odd – questions from passers-by have become commonplace.
Which is why, when approached by a man in Inverness, clearly under the influence of alcohol, Paralympic hand cyclist Darke got that familiar sinking feeling. "This drunk guy came staggering up to me," she says. "I thought: 'Here we go ...' But he looked at me, pulled out his mobile phone and showed me a photograph of his dog which had a little wheelchair on its back legs. He said: 'They wanted to put my dog down, but I insisted we got a wheelchair'."
There's a smile in her voice. "He may have been drunk but he was switched on. I thought: 'He's got what it's all about'. Then he leaned forward, grabbed my hand and asked: 'What's your mission?'. I said: 'Do I look like a woman with a mission?'. He replied that I did. So I told him about trying to get to the Paralympics. He shook my hand and said: 'Beat the Yankee.' I started laughing and said: 'She beat me last year, I've not beaten her yet'.
He disappeared then appeared a few minutes later and dropped some things in my lap. There was a can of Red Bull for energy, a stuffed toy Loch Ness Monster as a good luck mascot and a bar of chocolate for a treat after the race. He shook my hand again and said: 'Beat the Yankee'. I have never beaten her yet but I owe that man a win. I hope I can do it for him – and for Britain too."
Darke will get the chance to do just that when she competes in the 2012 Paralympic Games in London next week. The 41-year-old from Inverness will represent Britain in road race and time trial – and has set her sights on winning gold.
Perhaps most remarkably Darke, a former geologist, only started to hand-bike seriously in 2009. She began racing the following year and was selected for the GB Para-Cycling team. She took bronze in the Para-Cycling World Championships in Denmark last year, and has claimed silver in no less than four Para-Cycling World Cup events.
While her achievements are impressive, Darke's back story is equally compelling. A born adventurer, she climbed Ben Nevis at the age of seven, cresting Mont Blanc and the Matterhorn at 20 before winning the Swiss Marathon the following year.
Then, in 1993, while climbing with friends on the Aberdeenshire coast, she fell from a sea cliff. Darke broke her neck and both arms, fractured her skull and severed her spinal cord. She was left paralysed from the chest down. A testing rehabilitation period followed and while it would have been easy to lapse into self pity, she got a stark wake-up call only three months later. "A close friend of mine died in a climbing accident. It made me think: 'Right, I'm still alive and here, he's not'. I felt I had to make the most of things."
She drew inspiration, too, from those around her. "There was one woman I met during my rehabilitation I call 'the banana lady'," she recalls. "She loved bananas and spent six months learning how to peel one again [after a spinal injury]. She couldn't move her hands and arms properly but she tried every single day until she finally did it.
"We all have our different challenges: one of my earliest after my accident was to simply learn to sit up in bed. Now it's to win a gold medal at the Paralympics. I don't think it matters how big a challenge appears to those on the outside looking in. My challenges may seem to have got bigger, but for me they are no different to those early days." It's 19 years since Darke's accident, almost half her life. Did she ever lose sight of where she was going and what she wanted to achieve? "I think I did," she concedes. "I didn't really know how I was going to rebuild my life. I was fortunate in the early days, though, that I had friends who were willing to go do crazy things with me and help figure out what to do next.
"I did everything from paragliding to canoeing – every sport you could imagine I threw myself into just to see what was possible. It was a huge journey but once you do one thing it makes you realise what is possible and you start to dream."
Darke set herself the goal of cycling across the Himalayas in 1997. She has since hand-biked across Japan in 2000, kayaked 1200 miles around the Canada-Alaska coast in 2003, skied across Greenland in 2006, and climbed El Capitan, a vertical rock formation in Yosemite National Park, in 2007. Were these aspirations Darke held before her accident? "I don't have this list of what I want to do," she says. "It's more about who I meet, which ideas come to me. It's completely random. I like a challenge so when someone says something isn't possible, I like thinking about how it could become possible."
I'm curious where that formidable drive comes from. "You are made how you are," she says simply. "It's something I have always had – long before my accident. If I didn't have this then I would probably have never fallen off a cliff because I wouldn't have been pushing myself so hard as a climber.
"I don't know where it comes from. I love having adventures. It doesn't feel like I'm battling or pursuing some sort of huge, determined mission. I'm just doing what I do."
Her partner Andy Kirkpatrick, 41, is a writer and mountaineer. The couple met while skiing across Greenland in 2006 and got together the following year. Kirkpatrick and Darke's stepchildren, Ella, 13, and Ewen, 10, have had to learn to adapt to her punishing training schedule.
"Every single day there is a plan: whether it be training hard or resting to be ready for the next session," she admits. "That has a huge impact, not least on family and friends. Every time I want to do something I have to check my training diary to see if it will fit.
"Anywhere I go with family we have the bike in the back of the car. I will often end up training in hotel rooms or wherever I happen to be. Last year we were camping in Europe and I was training in our tent in a turbo trainer. It takes over life – and not just my life but those around me too."
Darke has written two books, If You Fall, and her recently-published second, Boundless. "I enjoy writing, I find it therapeutic to use my brain for a change instead of my body," she says. "I'm not usually good at sitting still. If I'm not on the bike, I'm going to the gym, swimming or meeting friends to do something active.
"I've had to learn to rest better as it's an important part of training, so I'm to be found lying on the sofa quite a lot these days. I've been watching what I call spine tingling films, inspirational stories that give me a bit of energy like Gladiator and Rocky IV."
She makes no bones about the gruelling sessions required to achieve her Paralympic dream. "I have trained my backside off for four years," says Darke. "I have committed everything to it and given it my all. I'm up there in the mix but still an underdog in terms of the gold. People can sometimes have this view about the Paralympics that the standard isn't quite there, but for my sport it certainly is."
Her biggest medal chance will come in the time trial. "We are split into different disability categories and in the time trial I'll be in my category whereas in the road race we are all women lumped together," she explains. "I have quite a high level of disability, so I will have a bit of a challenge in the road race as I will be racing against people who have all of their abdominal muscles."
Being a good time trialist, she says, is as much about strength of mind as body. "It's about knowing your body well enough to know how hard to push it without overdoing it," says Darke. "If you set out too fast you will run out of gas later on, or if you start too slow you won't get the time you need. It's a fine line. Am I going too fast? If the answer is yes, you back off; if it's no, you go faster; and it's maybe you have probably got it right."
As for the Yankee? "The main American in my category is Marianna Davis," she says. "Then there's the current world champion, a Swiss rider called Ursula Schwaller. Those are the main ones to watch out for."
Before she goes, I ask her about anything she would have done differently. Darke sounds incredulous. "I don't do regrets. You have got to look forward and make the most of what you have." Which, a week from now, will hopefully mean a medal around her neck.
The London 2012 Paralympic Games road cycling takes place from September 5-8. Karen Darke's book, Boundless, is £14.50 including P&P. Visit www.karendarke.com