Prime Minister (Doomcloud)

The Third Doctor, Sarah Jane Smith and Brigadier Lethbridge-Stewart met the Prime Minister at 10 Downing Street and warned him about the galactic cyclone approaching the Earth as a poison cloud. The Doctor advised that he and the chosen survivors of the United Kingdom retreat to emergency centres against nuclear attacks, to which the Prime Minister responded that he would prepare the necessary lists.

According to another account, the Prime Minister was visited by the Fourth Doctor, Joan Brown and General Maxwell-Lennon. (COMIC: Doomcloud)

Behind the scenes
Harold Wilson was the Prime Minister in the real world when this story was published in Summer 1974.