West Ham vs. Millwall is definitely the most heated rivalry in English football, much bigger than any of the rivalries between the big 4 and even bigger than Arsenal vs. Tottenham (its probably the biggest rivalry in Europe, but it is underpublicized because they are both small clubs). These guys have only played each other 24 times in the last 100 years so when they get an opportunity to play each other, it produces fireworks.


http://soccernet.espn.go.com/news/story?id=670607&sec=england&cc=5901