If Mo Farah wins the 5,000 metres tonight in Moscow he will have completed the 'double, double', winning gold medals in both the 5,000 and 10,000 metres at the Olympics and the World Championships.
Earlier this week Farah became the first British man to win a world title in the 10,000 metres but does that put him on the path to athletic glory? Some of the most famous British athletes have spoken to The Telegraph to have their say:
Farah took to Twitter ahead of the race, posting this picture:
There has been mixed reaction on social media to whether Farah could be the greatest athlete. There were generally positive views on Twitter:
While on the ITV News Facebook page, some readers disagreed:
In The Guardian Barry Fudge who looks after Farah at the major championships says completing the 'double, double' will be harder in Moscow than in London 2012 because he has less time to recover during finals.
At the Olympics there were 7 days between events whereas at the World Championships there are only 6.