London earned the nickname “The Fog City” due to its historical reputation for heavy smog, which is a type of air pollution that results from a mixture of smoke and fog. The city’s weather conditions, combined with its industrial pollution in the 19th and early 20th centuries, led to the formation of persistent and dense smog that was infamous at the time.

The Great Smog of 1952, also known as the “Big Smoke,” was a severe smog event that blanketed the city, causing significant health problems and deaths. It was primarily caused by the massive amounts of pollution from factories, coal-burning homes, and vehicles in the city. The weather conditions at the time, including cold temperatures, stagnant air, and a layer of fog, exacerbated the problem, trapping the pollution close to the ground and creating a thick, soupy haze.

After the Great Smog, the UK government passed the Clean Air Act in 1956, which was a significant step towards reducing air pollution and improving air quality in London and other cities. Over the years, London’s air quality has greatly improved, and while the city still experiences periods of fog and pollution, they are not as severe or as common as they once were. However, the historical association with smog and fog has led to the enduring nickname “The Fog City” for London.