THE Great Smog, in London in 1952, was four days of the densest air pollution ever caused by the uncontrolled burning of coal. The Capital was blanketed to a standstill, and 12,000 Londoners later died early from the resulting lung problems.

There followed big changes in the way we heat our houses and produce electricity, with coal fires giving way to central heating, followed by nuclear power stations and North Sea gas replacing much of the coal.

However the EU response to air pollution has moved on from reduced visibility and carbon based fragments to focusing on minute particles of nitrogen dioxide, NO2. At this particulate matter size some 40 of them would fit across a human hair, and once in the lungs they lead to over 40,000 early UK deaths every year.

The problem is that a diesel engine produces ten times more of these minute particles than an equivalent petrol one resulting in high concentrations in large cities with diesel buses, lorries and cars raising the pollution to excessive, and often illegal, levels.

Not long ago diesel cars were strongly promoted to reduce the amount of climate warming CO2 as they covered more miles per gallon, and now the national fleet is half diesel rather than just the fifth it was traditionally.

But this means we now breach the EU limit for atmospheric NO2. Indeed London exceeded the limit for the whole of 2017 by January 5, even worse than the first eight days it took in 2016.

The EU has acted, prompting Paris to ban older diesels, and with Athens and Madrid it will be diesel car free by 2025. However the UK is struggling with plans for just five clean air zones out of a possible 38 and so it’s likely to be back to court, for the third time, to encourage action.