They report that on a scale of 1-6 (6 being with the highest category of pollution), no places in Britain measured a 6 and, less than 1% measured a 4 or 5. 3/4s of the hot spots with the worst ratings are in London.
To top things off, the BBC article tells us that Government estimates on NO2 don’t take into account that as a car gets older, their harmful emissions reduce.
As a nation we’re cracking down on diesel cars as they produce more NO2 than petrol cars, but the flipside is that diesels produce less CO2 (a greenhouse gas), than petrol cars. So by my reading of the BBC article, we’re trying to eradicate diesel cars from the whole of Britain because of a predominantly London issue, and on Government estimates that might be a bit dodgy.