The 2 hour marathon is the new Holy Grail of international sport in the way the 4 minute mile was 60 years ago. Now BBC reporter and marathon runner Chris Dennis is asking whether it's physically and mentally possible to run 26.2 miles in 120 minutes.
Chris poses the question - will the 2 hour marathon be the next great sporting barrier to be broken or will it remain beyond human endeavour? And he recognises that this poser polarises opinion among athletes, sports scientists and commentators worldwide.
In a 1 hour special on Radio 4 tonight at 8.00pm Dennis talks to the current world record holder Haile Gebrselassie and asks him what it felt like to run the distance in 2 hours 3 minutes 59 seconds and how close to the limit he pushed his body. He also questioned the legendary Ethiopian about his belief that the two hour barrier will be broken in the next 20-30 years.
Olympic champion Sammy Wanjiru disagrees with Gebrselassie and says why.
Hear this fascinating report and exchange of views tonight on Radio 4.