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[Grahamm]

I believe you mentioned that the prevailing wind is from the south west, so where would all the pollution from those suburbs go?

The less visible but equally toxic pollutants of carbon monoxide, nitrogen dioxide, ozone, benzines, and aldehydes continue to spoil London’s air. Traffic fumes and other exhausts are liable to become trapped between the surrounding hills and below a stagnant capping mass of warm urban air at an altitude of about 3,000 feet (900 meters), causing immediate increases in eye irritation, asthma, and bronchial complaints.

Britannica