At 20, how well is the World Anti-Doping Agency doing?

It’s 20 years since the World Anti-Doping Agency was formed. Its ambition was to make sport clean, to clear out the drug cheats. This week in the Polish city of Katowice, a major conference is taking place to celebrate its achievements. But the agency’s credibility has been questioned over the way it handled the Russian doping scandal. And it’s an issue that issue looms large over the proceedings. The BBC’s Alex Capstick reports.