Inferno universe

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

19th century
The Confederates won the American Civil War.

20th century
Joseph Stalin was, in this world, a Menshevik. The British Royal Family had been executed for undisclosed reasons at some point prior to the 1940s. The Japanese successfully built their Asian Co-Prosperity Sphere. The Second World War never happened since Europe was divided into allied British and Russian spheres of influence to intimidate Adolf 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 from attack and to intimidate subversive groups and enemy nations. The reasoning was since the Moon could 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 its responsibilities. In Britain, the state security militia was the Republican Security Forces. Many of its members were the parallels of British UNIT members, including Alistair Gordon Lethbridge-Stewart, Elizabeth Shaw and John Benton. (DW: Inferno) Shortly after the Doctor's unplanned arrival in this universe, an accident at Stahlmann's project devastated the entire surface of the planet within thirty-nine hours. The only survivors were those in bunkers, space stations, or on the Moon. (PDA: The Face of the Enemy)

At the time of the devastation, 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)