When the runners at the 2012 London Marathon begin their 26.2 mile journey they won't be just trying to win one of the world's best races, they will be competing for spots in the summer Olympic games this year which also take place in London.
Louise Damen is one of several British athletes hoping to have a good performance at the marathon and qualify for the English team in the Olympics.
She told BBC:
"I've probably experienced the two ends of the spectrum.
"I had a great experience on my debut in London and then a horrible one in Yokohama. It taught me you can have a brilliant build-up but things can go wrong over 26 miles."
Damen's first ever attempt at a marathon came in London in 2011 so she's familiar with the course, which should help here this spring.
Damen, like all other brave athletes who run marathons often, know that endurance and stamina are two key components of a good performance.
The London course is difficult, but the added pressure of possible Olympic qualification will add to the challenge of the event.
With a spot in the Olympics at stake in London we could see a thrilling finish to the marathon because if there's anything that will motivate runners to perform well, it's the opportunity to qualify for one of the world's most amazing events.