Great Smog of London

The Great Fog of 1952 happened in London between 5 and 9 December 1952. During these four days, a dense smog settled on the city, causing thousands of deaths. The smog was caused by lingering fog combining with smoke from coal fires. (PROSE: Amorality Tale) It was worsened by the Fumifugium. (AUDIO: The Creeping Death)

The Third Doctor and Sarah Jane Smith were in the city when the smog happened, (PROSE: Amorality Tale) as were the Tenth Doctor and Donna Noble. (AUDIO: The Creeping Death)

Between four thousand and twelve thousand of Londoners died in the span of four days due to the smog. (PROSE: Amorality Tale)

According to Lizbeth Hayhoe, no one at Torchwood One was interested in having London's smog investigated, "not since that business in '52". (AUDIO: The Man From Room 13)

Behind the scenes
Though the name "Great Smog of London" is never used during The Creeping Death, the date in which the story is set and the Tenth Doctor's comment that the smog happening was the worst London had ever seen makes the event recognisable enough. Amorality Tale refers to the event as the "Great Fog of 1952".