Since this is going to be my first contribution to the site I'll be running a US Civil War alternate that will hopefully differ from many you've read before. Enjoy...
The House of Lords, London, November 27th 1861
AS per usual, chaos reigned in the house of Lords. "We cannot interfere with another nations sovereignty!" Screamed a Tory from one side of the room. "Then are we to allow chaos and oppression?" A liberal replied. "No, we are to allow slavery if the honourable gentleman had his way!" The Prime Minister, The Viscount Palmerston, rubbed his brow. He was growing tired of this bickering. "GENTLEMEN!" He bellowed and silence fell. "Are we to allow this insult to go unchallenged?" A series of "No!"s echoed throughout the room. "Gentlemen, we are Great Britain, are we to bow the United States? No we are not! Earlier today I met with her majesty and she told me that unless we... fine gentlemen, react in a way fitting of strong Englishmen, she should see as as of less use than a court of Frenchmen!" That gathered some laughs and less jeers. "The American President, a man who calls himself "Honest Abe" has issued us this insult!" The Viscount thrust a piece of paper into the air. "No apology, no justice! Nothing but arrogance! Gentlemen, I will not let some colonial revolutionary soil my great nation! Will you?" A roar of support flew from the men around him and Viscount Palmerston smiled.
This is just a basic set-up, the general idea is British intervention in the Civil War following the Trent Affair but I intend it to spiral out from there.