The Mayor of London, Boris Johnson, had what was described as a "near-miss" with a lorry while riding his bicycle in east London.
The incident, caught on a private security camera, happened as the mayor cycled in a street in Limehouse.
As a lorry overtook him its back doors flew open and hooked the windscreen of a parked car, dragging it for several yards before smashing into another.
The mayor said it reinforced the need to make London safer for cyclists.
The footage apparently showed Mr Johnson cycling around the corner of the street with a group of transport advisors, who were also on bicycles.
They were in east London to look at potential sites for new cycle lanes.
After the crash, the mayor was seen scratching his head with his cycle helmet in hand as he crossed the road to survey the wreckage.
Witnesses said it was extremely fortunate no-one was seriously injured.
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