Ask Paul Selby what keeps him going on his ultra marathons and he can't really explain. He'll say faith. Others add passion, courage and sheer determination.
Whatever drives him, Paul is a running legend in his adopted South African homeland.
He runs for pleasure and charity. His business is designing and producing finisher medals for marathon runners worldwide. He launched the1000km Challenge to recognise those who run huge distances every year training for the 90km Comrades Marathon. This year he tackled his 25th consecutive Comrades and 640th marathon - despite badly breaking his ankle while training last October.
Distance isn't an issue for this Englishman. In 1999 he completed a 180km back-to-back Comrades Marathon, raising 200,000 Rand for charity.
In 2003, he joined a small team running 1000 miles in 1000 hours around the London Marathon route, raising money for charity.
They covered the course 38 times in one-mile hourly segments day and night for six weeks. At the end, they had to run the official London Marathon to determine the winner.
Comrades is the highlight of the year for distance runners in South Africa.
"It's a life-changing experience," says Paul. "It is so tough. You hurt; you struggle and suffer; then you see the next runner in the same plight. Comrades is a life adventure in one day."
Sadly, this year, Paul had to quit with just 20kms to go. While his ankle held up, he found the lack of distance training affected his strength in other ways.
Paul's completion of the 1000km Challenge was also under threat after his injury.
Runners aim to complete at least 1000km in official races in the year from Comrades to Comrades. For this they receive a bronze medal, with a portion of their entry fee donated to charity. Other medals are presented to runners who cover greater distances in the year.
One of Paul's proudest achievements was receiving a Spirit of Comrades Award in 2007, acknowledging his support of the race, his back-to-back Comrades run, the 1000km Challenge and his penchant for helping struggling runners along the route.
Charitable causes are something Paul feels strongly about. In the country that has given him a home, a wife, a family and a living, he believes it is important to give something back.
The marathon medal business grew out of his engineering company, when Paul discovered a flair for design combined well with his engineering skills.
Now he produces more than 2 million finisher medals annually