There's nothing quite like a full-blooded rivalry in sport. Not only does the thought of two sides having just as much to lose as they do to win add to the excitement, but derby clashes inevitably carry the unspoken air of unpredictability.
Though it can be fairly argued that rivalries in any sport are an immediate draw for the neutrals, there's something extra special about them in football.
Be it on the club or international scene fans are given plenty to drool over when a game comes along which offers that little bit extra, and it's no surprise to see those who follow the respective sides clashing in the build up to the event in question.
But which footballing rivalry stands out as the most bitter? It's all to easy to run through the hundreds of sour-relations between two clubs, but it's more difficult to pick those which stand head and shoulders above the others due to a number of different factors.
On the eve of England vs Scotland we've decided to throw together the top five most bitter rivalries in football, sharing matches from all around the world.
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Click on the 'begin slideshow' button to see our selections, and let us know your thoughts in the comments box below...