Seventy years ago, London choked. For five days in December 1952, a toxic smog smothered the city. Visibility collapsed. Transport failed. Thousands died. It was not a natural disaster. It was the product of policy failure.

Out of that catastrophe came one of the most important environmental laws in UK history: the Clean Air Act 1956. It was a turning point. It showed that science, when taken seriously, can transform public health.

But the story does not end in 1956. Because the same forces that delayed action then continue to shape air pollution policy today.

The Clean Air Act was born from evidence. The Beaver committee’s 1954 report, named after its distinguished chairman, Sir Hugh Beaver, made a simple but powerful case: air pollution was not inevitable. It was a social and economic problem that could be solved.

The law followed. Smoke-control areas were introduced. Dirtier fuels were phased out. Emissions were regulated. Over time, air quality improved dramatically.

This model spread globally. Evidence-led regulation became the foundation of air pollution control in many countries such as the US, Japan, Germany and Australia. Monitoring improved. Health effects became measurable. Courts began to hold governments accountable.

Read more: These colourful diagrams show how air quality has changed in over 100 countries around the world since 1850

Major global successes followed this template. The Montreal protocol, a landmark treaty agreed in........

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