On the eve of the World Athletics Championships in Eugene, Oregon, one of Track & Field's best-loved stars, Sir Mo Farah, revealed a secret which upended everything we thought we knew about his life. Producer Jessica Yarmosky relays the story he tells in a BBC documentary The Real Mo Farah and speaks to 1500-meter champion Jake Wightman and Sunder Katwala of British Future about what this revelation means for running, Britain, and Farah's legend.

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