"You're lucky you've caught me as I was about to go on a two-hour run to try to keep fit."
Having become the oldest Briton to scale Mt Everest when, in 2009 at age 65, he reached the summit of the world's tallest mountain, Sir Ranulph Fiennes is clearly not allowing his advancing years to slow him down.
With a new and punishing training regime that has even seen him running up and down stairs at airport departure lounges, he is about to head out on one of his daily marathons when I call him at his Cornwall home.
"Taking exercise when you're feeling lazy isn't something to be frightened of," he says. "It's just something you've got to be a bit strong-willed about at the time."
Known as the world's greatest explorer, the Berkshire-born adventurer does admit his body is finally showing signs of wear and tear after decades of mountain climbing, polar expeditions and other feats.
Fiennes certainly confronts a few demons in his latest book, Fear. Subtitled Our Ultimate Challenge, it examines the often trivial and sometimes major things we are all afraid of.
"I was asked to write the book because the publisher thought that I was an expert on fear," he says. "But fear is such an abstract concept, and it can encompass everything from the fear I remember having at one point when my wife was driving me to the more hellish fear that a lot of people have suffered in terrible places likes Auschwitz."
From the dramas of being a pupil at exclusive English boarding school Eton and then a soldier in the British army, Fiennes connects the various examples of fear in the book to his personal experiences.
"It can come out through your genes or something that might have happened to you when you were little. There are certain things that come out of that age-old animal fear, such as fight or flight or freezing, in stressful situations. I've gone into that with help from psychologists, as well as things like people who have Post Traumatic Stress Disorder."
It includes the various ways - from the tragic consequences of cyber-bullying to the larger impact of terrorism - that we can be scared out of our wits. He says there are at least a dozen identifiable forms of real fear in the book and they are different to one another in many respects.
"The book is full of chapters on the dreadful fears people have felt, which in some cases includes my own fears, such as vertigo. That's basically how the book is put together, so if you don't want to go to sleep at night, you should read it just before you go to bed."
Unfortunately, embarking on Fear hasn't necessarily helped Fiennes overcome his own personal fears.
"My fear of someone I love dying hasn't been affected by writing the book and my fear of my own dying certainly hasn't been either. Out of the two phobias I've previously had, one of which was of spiders, I explore how I managed to get rid of that through confrontation.
"But I also explain, in a later chapter, how I attempted to get rid of my other phobia, which was vertigo, and that wasn't so successful, so writing about it didn't help anymore than climbing nasty mountains has helped."
Wanting to avoid appearing foolish in front of some of his military colleagues when a wolf spider landed on his ankle helped Fiennes to come to terms with his arachnophobia.
"The fear of losing respect turned out to be greater than the short-term fear of having a nasty creepy-crawly on your body. My natural reaction when that big spider first came on to my leg was to crush it quickly with a stone or a fist, and probably scream or make a noise in the process, which I definitely would have done if I'd been by myself."
Describing it as "the only fear I have that I know definitely has changed", he hasn't exactly come to terms with his fear of death even if, after suffering a massive cardiac arrest in 2003, he's more realistic about it. "I had a double bypass and was on a life support machine for three days," Fiennes recalls.
"They couldn't start my heart ticking again, but on the 13th time after three days, it eventually did tick. But it might still not have started by the 14th time or the 20th or 200th, so at some point you're obviously going to be dead."
Fear - Our Ultimate Challenge
By Ranulph Fiennes