He is quick to add: "I am not and never have been an elite athlete. I think of myself much more as a weekend warrior, albeit an obsessed one."
His obsession will take him on an epic adventure that aims to raise awareness and funds for mental health on both sides of the world.
What has inspired you to run 24 marathons in 14 days?
I love setting myself big hairy audacious goals and, having already proved that I can do seven tough runs day after day [In 2009, Law made history by becoming the first person to run New Zealand's seven mainland Great Walks in seven days, a total distance of 360km], it was a natural progression.
The location of this run is significant. It is the part of the world where my parents were raised and where they spent many happy years of retirement before both passing away early last year. They were great walkers and had completed many sections of the trail themselves over the years. So, in a sense it's a spiritual journey and part of my ongoing grieving for them.
But my biggest motivation is the cause that we are running for. Ever since losing my brother-in-law Max, who took his own life some 17 years ago, I've been very aware of the devastating effects that mental illness can have. I know from personal experience that goal-setting, running, and spending time in wild places is a very uplifting experience that can do wonders for one's mental wellbeing.
The terrain is incredibly tough - many people will think you are mad taking that on.
I guess when people think of the UK coastline they think of it being fairly flat but the reality is that we have an endless succession of climbs and descents. In total, we have 35,000m of ascent, equivalent to climbing Mt Everest four times from sea level, over the entire run. And what goes up must come down, often in pain. So yes, people might think we are mad but I relish the challenge of the hills, which I would always prefer to the tedium of a flat run.
How are you going to prepare for that?
Volume has been the key to my training. This year I have run close to 2000km, at an average of over 100km a week. I've also incorporated Pilates, core strength exercises and regular massage into my regime and these have been a massive help. To condition myself for the hills I have done an extraordinary amount of strength work and hill repeats. I recently ran up and down North Head in Devonport 148 times over the course of a day - the equivalent of climbing and descending Mt Everest from sea level - almost 9000m of vertical ascent and the same of descent. That has given me an enormous psychological boost.
How do you know your running mate Tom Bland and how do you think you'll handle the challenge together?
I've never actually met Tom. I discovered his ambitions to run the South West Coast Path by accident while surfing the internet one evening over a year ago. Since then we have Skyped and emailed frequently and got to know each other at least a little bit. I'm confident that we will hit it off but you never know quite how it's going to turn out, especially when we are tired and stressed, so fingers crossed.
Why do you think mental health is a big issue in New Zealand?
We have a culture of playing our cards close to our chests. We are scared of people thinking that we are in any way weak. All that is a recipe for mental health issues and I think that is why in New Zealand we have such a high incidence of such illness. A big part of CoastPathRun is to encourage people to talk openly about how they are feeling. Depression is no more a sign of weakness than having a cold. We tell people when we have a cold, we've even been known to exaggerate how bad it is and we'd be a lot healthier as a nation if we felt we could talk.
Is this run a metaphor, that even though it's really hard where there is a will there is a way?
Yes. In many ways our two-week fight with a long-distance trail is analogous to the battle against depression that so many people face. There are ups and downs, highs and lows, tough times and despair. But if we seek support from those who care about us and believe in us, if we refuse to give up, then just about anything is possible.
What advice do you offer to people looking to take on challenges in their own lives?
The key to success is breaking the challenge down into manageable chunks. We'll seldom be looking more than 10km ahead, but as each of those small goals is knocked off so our belief that the 'finish line' really is attainable will grow. This applies to all kinds of challenges we face in life.
