Positively scandalous: A history of drug-taking at the Olympics

Our take: Stress, training and the need to succeed sometimes take too much of a toll on Olympics athletes, especially when it drives them to take drugs to help improve their performance.

They may not be the only competitors at these games to be caught by the doping police, though it could be a while before the final tally is known. All blood and urine samples taken in London will be kept for eight years, to allow time for testing technology to catch up with the drug-takers.

The best-known drugs cheat on our chart of shame is represented by the Canadian flag in the athletics section. Ben Johnson won the 100m at Seoul in a world-record time, but was disqualified three days later after failing a drugs test, sending the athletics world into turmoil.

Read more about Olympic drug scandals on The Economist .