Sir Oswald Mosley was a British politician in the 1920s and 1930s who held fascist beliefs.
In December 1936, King Edward VIII planned to dissolve Parliament and replace it with one more loyal to him, with the help of fellow Nazi sympathiser Mosley. The plan was thwarted by the Sixth Doctor, Peri Brown and Winston Churchill. (PROSE: Players)
In 1940, Mosley was imprisoned for advocating the belief that the United Kingdom should ally itself with Germany in World War II.
In an alternative timeline in which Germany won the Second World War and proceeded to conquer the United Kingdom and the rest of Europe by 1941, Mosley was released from prison and became Prime Minister of the United Kingdom, replacing the executed Churchill. (PROSE: Timewyrm: Exodus)