The Green Party has published this picture, claiming that is shows "why we need a very low emission zone for central London ASAP, not in 2020".
It is a map of nitrogen dioxide (NO2) pollution in the congestion charging zone, put together by Assembly Member Jenny Jones.
It is based on NO2 emissions modelling carried out by Kings College London, not on actual readings.
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Just off Fleet Street stands a famous tiered tower. Designed by Sir Christopher Wren, it became the inspiration for the wedding cake.
The president of the respected Royal Institute of British Architects became the latest high profile figure to enter the row.
The victim, thought to be in his 40s, was attacked in Bromley at around 11:30am. His condition is still unknown.