The Mayor showed off one of London's "Boris bikes" in Beijing, joking about the cycle hire scheme being "communist".
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A Met Police officer was left red-faced after attempting to stop a cyclist riding along a dedicated cycle path.
The number of people allowed into official spectator areas will be cut by a fifth with just 100,000 tickets available.
The mayor was being challenged by Labour following his selection as the Tory candidate for the safe seat of Uxbridge and South Ruislip.