The Great Smog of London in the 1950’s. Killed up to 12,000 and injured thousands more. A mysterious pea soup fog mixed with coal smog that covered the city for days. In the fog there was a crime wave where criminals were hidden by the fog and police couldn’t operate, and there was even one famous serial killer who killed in the fog. John Reginald Christie. A book about it called Death in The Air is very interesting and worth a read.