As the morning progressed, a clear blue sky descended into a hellish yellow-brown haze. Londoners were used to smog, but this was different. Visibility was cut to mere metres. People in the Isle of Dogs reported not being able to see their own feet.
The smog settled on Friday 5 December and when it lifted, four days later, 4,000 people were dead. This is almost certainly a substantial underestimate.
