Why do football fans decide to support one club over another in cities where intense, deep-seated rivalries exist? What makes them choose: family ties, geography, politics, religion or perhaps race? Rivals Game author Douglas Beattie spent two years discovering what lies at the heart of Britain's greatest derbies. Beattie takes the reader to the matches that have long been seen as passionate, divisive and vitally important to the entire cities in which they are played. These are the games that have a history of violence, feuding, social unrest and bigotry. But what is the truth about their origins and how does the enmity, so often displayed by supporters and gleefully reported by the media, manifest itself in an era which sees top clubs funded by billionaire chairmen and awash with TV revenue? With tensions rooted in Britain's industrial strength, and discord stretching back as far as the English Civil War, Douglas visited Sheffield, Birmingham, north London, Manchester, Liverpool, the North East, Edinburgh and Glasgow to uncover the answers to questions such as: why do the citizens of Sheffield call each other 'Pigs', who was Wallace Mercer - the man who divided Edinburgh, what is it like to meet Birmingham City's Zulus, why does the shadow of the Hillsborough disaster loom large in the history of the Merseyside derby and what caused Celtic and Rangers to go from best friends to sworn enemies?