Okay.
This is written from an outsider's POV (American), so forgive my ignorance.
In 1842, John Francis successfully kills Queen Victoria. This eventually leads to the Young Irish Rebellion succeeding, and the Declaration of the British Republic in 1848.
This goes without much hassle until 1914, and with Germany invading Belgium, drawing Britain into the war.
The war ends as it does OTL, but Britain sees a massive change with the formation of the Communist Party of Great Britain in 1920.
In 1928, the Great Depression hits, and this leads to a massive surge in both the British Union of Fascists and the Communist Party of Great Britain. In the elections of 1932, the British Union of Fascists is surprisingly defeated by the Communist Party of Great Britain, which has General Secretary Harry Pollitt elected President. He gains power more and more frequently, and in 1936, wins the election unanimously, declaring an end to the Republic and creating the People's Republic of Great Britain.
The primarily fascist Scotland (ITL) is furious at this, and declares themselves independent from the People's Republic.
This might or might not be really ASB, I'm not British as I said before.