Grosvenor Place, which runs alongside the Queen's London residence, had the highest level of the toxic gas nitrogen dioxide in 2012.
Researchers found 152 milligrams of the gas per cubic metre of air, with a main contributor being diesel engine fumes. The EU legal limit is 40.
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Police have released CCTV of a man they wish to identify after an assault in Newham.
Piccadilly lights were switched off for modernisation work to take place. It's the longest time the lights will be off since the Blitz.
But renters have been warned that the trend is unlikely to continue.