The brilliant warrior-poet Dante Alighieri was born in Florence, in the district or quarter known as San Martino in May or June 1265. In later life, he was banished from his home in Florence by his enemies and began to write The Divine Comedy: Inferno, Purgatorio, Paradiso. This amazing poem described all the terrors, pains and wonders of Hell, Purgatory and Paradise. Dante had an imagined companion - the Roman poet Virgil, and together they examined the results of gross sin and the forgiveness of God. In this book we are concerned with just a few lines of Inferno, albeit of foremost importance, concerning the horrendous butchery of a vengeance killing in an Italian church during Holy Mass. These lines have a surprising mention of the River Thames in England and so they reflect another bloody conflict - the war between the King of England, Henry III, and the French warrior Simon de Montfort. The book also explores the mythical idea of Rivers of Blood and the English conspiratorial phrase: 'He is up to his neck in it.' The author puts forward a theory showing why Dante may have used particular words in the verses of Inferno. This history details how Earl Simon de Montfort was killed, how his sons Simon and Guy pursued a vendetta against someone who was innocent - Henry, King of the Romans, and how the various Rivers of Blood stemming from the Holy Blood of the crucifixion of Christ and the bloody de Montfort vengeance killing merge into an historic saga of hate and madness.