Prime Minister (Doomcloud)

In 1974 at 10 Downing Street, the Prime Minister was warned by the Third Doctor, Sarah Jane Smith and Brigadier Lethbridge-Stewart 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
The real world Prime Ministers of 1974 were Edward Heath and Harold Wilson.