When dense smog cripples London for days and creates a serious health hazard, Churchill's inaction leaves him vulnerable to his political enemies.
- This episode features "The Great Fog of London", which occurred over five days in early December, 1952 and resulted in the deaths of thousands of Londoners. The fog, sometimes known as the "London Peculiar" was not actually fog, but heavy coal smoke accumulation caused by lack of wind and other atmospheric conditions that prevented the smoke from dissipating. These periods of fog were common in London and other major cities in the decades when coal was used to heat homes and make electricity. The problem was compounded in London, where four coal-fired power plants across greater London spewed voluminous coal smoke into the windless air.
- The decades of coal heating and coal smoke such as that featured in the episode did considerable damage to the granite and marble buildings of London, where residue would accumulate on their exteriors. The oily smoke included highly acidic sulphur dioxide, which both damaged the human respiratory tract and ate into the surface of buildings all over London, leaving a black residue. In the 1980s and 90s, London began a widespread clean-up of historic buildings, removing the coal residue and bringing the buildings back to their former glory.