Have, with a POD of anywhere after 1900, at least part of what is now the United Kingdom governed by a regime that could be called the "Red Celts" or "Red Picts" for at least one year.
A regime of Red Celts/Picts/... must include:
1. an extreme, skewed variant of Communism or far-left ideology in any form
2. The wish to return to pre-industrial, "Celtic" idealised society with agriculture and, if possible, (pseudo-)Celtic rituals dominating.
3. Genocide, mass murder, and/or ethnic cleansing used as means to reach the goal.
So, basically: Create a British Pol Pot!
A regime of Red Celts/Picts/... must include:
1. an extreme, skewed variant of Communism or far-left ideology in any form
2. The wish to return to pre-industrial, "Celtic" idealised society with agriculture and, if possible, (pseudo-)Celtic rituals dominating.
3. Genocide, mass murder, and/or ethnic cleansing used as means to reach the goal.
So, basically: Create a British Pol Pot!