When I was a kid St Patrick's Day wasn't really a celebrated thing (the UK and the Republic of Ireland had had bad relations due to The Troubles since the early 1970s, and there were bomb attacks by republicans in the UK even as late as 1997). But now that's all over, it's becoming more and more popular in the UK to celebrate it. Most people wear green and dress up to go to the pubs in the evenings with friends.