Now, a lost letter from Pope Alexander II sheds more light on how it all came about. It shows that the battle for England’s crown was shaped by a bitter power struggle between two rival popes, who both claimed authority, in the 1060s. England’s support for the rival papal faction may have persuaded Pope Alexander II to back William’s invasion, the newly discovered letter from the Vatican archives shows. The discovery followed an examination of overlooked excerpts from a lost letter by Pope Alexander II that was preserved in a medieval canon law collection held in the Vatican. “What this evidence suggests is that Pope Alexander II may have had political reasons of his own for backing the Norman invasion.”