The Party's timeline

In an alternate timeline, England was ruled by the Party by 1984.

As Amanda retold to Honoré Lechasseur, the "old world" ended on 21 January 1950. After she learned that Simon Brown worked on deciphering the atomic bomb's secrets for the British atomic weapons programme, their conversations of politics merged with that subject. They came to the mutual agreement that for the betterment of humanity, everyone should know the secrets of atomic weapons. Simon spread his knowledge to the world, and in retaliation, Joseph Stalin released his atomic bombs on the planet, and the Party took over.

Radford placed his actions as the sole factor for the creation of the new timeline. (PROSE: The Winning Side)

Behind the scenes
The timeline depicted in The Winning Side is the universe which George Orwell's novel Nineteen Eighty-Four takes place in.