What put an end to any serious possibility of britain recognizing the confederacy?

The United Kingdom of Great Britain and Ireland and its empire remained officially neutral throughout the American Civil War (1861–65). It legally recognised the belligerent status of the Confederacy, but never recognized it as a nation and never signed a treaty or exchanged ambassadors. However, the top British officials debated intervention in the first 18 months. Elite opinion tended to favour the Confederacy, while public opinion tended to favour the United States.