"the longest winter in history froze over the Thames"

The winter of 1819-20 was a very severe winter, with temperatures of -23°C recorded in Tunbridge Wells. The coldest London winter of the 19th century came a few years later on, in 1837-8, when central London reached an unheard of -16°C. Throughout the Victorian era the Thames froze over during several winters, and the longest winter was 1820-21: in May 1821 snow fell in London – the latest recorded snowfall until June 1975.

More on the history of British weather.