This file photo shows Tirunesh Dibaba of Ethiopia winning the women's 5000m final during the Samsung Diamond League meeting at Crystal Palace in London, in 2010. Friday's 10,000m final at the 2012 ... more 

This file photo shows Tirunesh Dibaba of Ethiopia winning the women's 5000m final during the Samsung Diamond League meeting at Crystal Palace in London, in 2010. Friday's 10,000m final at the 2012 London Olympics will be particularly fascinating as it has been built up as a duel between Kenya's world champion Vivian Cheruiyot and Dibaba, with both eyeing a middle-distance double less