evidence: Illegally-high levels of nitrogen dioxide were recorded at more than 250 sites in the east of England, it has emerged. [...] The figures, although illegally high, are a far cry from some of the readings found in central London where the average annual level of nitrogen dioxide (NO2) in Grosvenor Place, near the Queen's central London residence, reached 152 µg/m3 in 2014. Illegally high readings have also been frequently recorded in cities such as Leeds, Birmingham, Southampton, Nottingham and Derby, external.