As a natural athlete, the 34-year-old Parr is well versed in pushing himself to the limit. It was easier on the rugby field when he had teammates around him. But long distance, nay ultra-distance, running is way different. It is lonely and dangerous. This risk factor is what challenges people like Parr.

'In every ultra-marathon and endurance event, especially those in isolated and rugged environments, there is risk. This is precisely why people enter these races. If you want an easy event, go and run a road race or a city marathon. People want to compete in ferocious environments like the Gobi and the Sahara so they can then say, 'I ran an ultra in the desert',' says Parr.

Last month, four ultra runners taking part in a Racing The Planet event in Australia suffered serious burns when they were caught in a bush fire. Parr is pragmatic. He is one of those people who believe a calamity can happen any time, even when you cross the street.

'What happened in Australia was extraordinarily bad luck and there is no amount of individual preparation that can help in that situation,' Parr says. 'It's devastating for the runners and for the ultra community but it's also a cruel reminder that when you are out in these isolated, beautiful and fierce environments, you are at the mercy of nature. In my opinion, it is the responsibility of the individual competitors to understand that risk and to prepare accordingly.'

Parr has been busy preparing for the past three months. The Sahara, the world's second largest desert after Antarctica, is one of the most forbidding places in the world. Heat will be a constant enemy. Most of the distance will be run on sand, hard packed in places but loose in others. Sandstorms are a constant danger. But as Parr says, nature is something you have to take as it comes and you can only prepare for things under your control.

'To train for a race over 250 kilometres you have to do a lot of running and unfortunately there are no short cuts. In order to prepare properly you have to put the time in and that means getting out on to the trails and into the hills whenever you can,' said Parr, who works for sports marketing agency Fast Track.

'I've been running to work most days, and then do two 25-kilometre runs after work during the week and then a big one on Saturday of 40-plus kilometres,' Parr said.

'I also do spinning [exercise bike] classes three or four times a week which is a great cardio workout, but it's all about time on your feet and getting your body ready for the onslaught of running long distances for days on end.

'Sunday is rest and family day. The amount of training is tough, not just on me but on my wife and family as well but I am lucky as Katy is extremely supportive even though she thinks I'm mad. Without her, it would be impossible to commit the time to training and preparing properly,' says Parr, father of Milo, three and Ottilie, one.

Parr wouldn't have been into heavy-duty running if not for peer pressure from a friend, Rowley Aird, who coerced him into taking part in the Gobi March last year. But his love for adventure racing had been born a couple of years earlier when, soon after stepping away from playing rugby, he took up hiking the diverse trails in Hong Kong so as to stay fit.

'A few years ago I got roped into doing an adventure race with a friend in Macau and we did quite well. After that we decided to try another race in Singapore, and that was the first time I really started running the trails on a regular basis and training quite hard,' he said.

'Unfortunately, the Singapore race was a disaster as I arranged to borrow a bike from a friend and it turned out it was a road bike. I didn't have time to get another so had to try to ride the mountain bike trails on a racing bike. Unsurprisingly, I got a puncture after about five minutes and had to ride the bike with a flat for about 20 kilometres.

'We didn't win in Singapore but my enthusiasm for adventure racing and trail racing was born and I started doing more races and more running and it turned out that I wasn't bad, winning a few King of the Hills and Action Asia Sprint races.'

Parr entered his first MacLehose Trailwalker in 2008, finishing in 18 hours. The long-distance bug had bitten him hard. He did the MacLehose trail again the following year and shaved off four hours. The friend who had goaded him into his first adventure race, Aird, 'upped the ante' and egged Parr to run the Gobi March last year. He did, and ended up winning it.

'Fear was my motivation for my first ultra. Fear of the unknown, of how I would perform, of what lay ahead and of not letting people down who had sponsored me, backed me and challenged me to do it. I wanted to perform well and that drove me on to train as hard as I could. There is a great saying: 'It's not the will to win, but the will to train to win that counts'. That sentiment kept me going on the long, painful training sessions.

'My motivation for the Sahara is different. Now that I've done one I don't have the fear factor but there is the fear of letting myself down by not giving a good account.'

And as he'll be raising funds for Sparks, a charity that funds vital research into a host of paediatric medical issues which affect mums-to-be, babies and children, Parr will be given wings.

'When I'm stumbling across the Sahara and dreaming of air-conditioning and cold beers, during such low moments of the races, knowing that my pain is generating cash for such a phenomenal cause will be a huge motivator,' Parr says.

300km

The minimum distance Dan Parr covers in a week while training