Inferno universe

In one parallel universe, Great Britain was a Republic governed by a fascist regime.

History
In this universe, the Confederates won the American Civil War, Joseph Stalin was a Menshevik, the British Royal Family had been executed for undisclosed reasons at some point prior to 1943, the Japanese successfully built their Asian Co-Prosperity Sphere and the Second World War never happened since Europe was divided into allied British and Russian spheres of influence to intimidate Hitler into backing down from his sabre rattling. This world was effectively ruled by the Conclave, a parallel of the United Nations Security Council. The Conclave were based at Copernicus moon base to protect the delegates against the possibilty of attack and to intimidate subversive groups and enemy nations. The reasonining being that since the moon can be seen from all parts of the civilised world it would serve as a reminder that the Conclave was watching.

There was no direct parallel of UNIT, instead national military organisations undertook it's responsibilities. In Britain the state security militia was the Republican Security Forces. Many of it's members were the parallels of British UNIT members, including Alistair Gordon Lethbridge-Stewart, Elizabeth Shaw and John Benton. (DW: Inferno) Shortly after the Third Doctor's arrival in this universe, the incident at Stahlman's project devastated the entire surface of the planet within thirty-nine hours, the only survivors being those in bunkers, space stations or on the moon. (PDA: The Face of the Enemy)

The Doctor's parallel self was the leader of Great Britain, he was killed when the fallout from the disaster at Eastchester destroyed London. (NA: Timewyrm: Revelation)