Top athletics coach faces doping claims

One of the world's best known athletics coaches is at the centre of doping allegations following a BBC investigation.

Alberto Salazar is accused of violating anti-doping rules. Among the allegations, it is claimed he was involved in doping the American long distance runner Galen Rupp.

Salazar trains both Rupp and Britain's Mo Farah at his base in Oregon in America.

But there is no suggestion that Farah has broken any rules.

The allegations against Salazar have been made by a number of former athletes and staff. Salazar and Rupp both strenuously deny any wrongdoing.

Mark Daly has this exclusive report.