Swifter, higher, stronger is the Olympic motto but has the athlete's ultimate dream to win gold created a culture of world-class cheats? Reporter Tom Mangold talks to Olympic athletes en route to this year's games who admit to having taken drugs and talks to the steroid gurus to reveal the hidden underground network behind the glamour of the centennial games.

(Note: because Panorama is a topical programme and likely to react to events in the news, the above programme is liable to change)