1298: Alexander of Wells watches William Wallace's army across the field at Falkirk. Hours later, he is dead, cut down by the Scots.

1381: Hated collector of the Poll Tax, Robert Hales, is dragged from the Tower of London and executed, his head paraded through the streets before being placed on a spike on London Bridge.

1490s: John Kendal sends coded letters to Perkin Warbeck's supporters and hires an astrologer to murder Henry VII.

These men were not scheming lords: they were Knights Hospitaller. Commonly known as warrior monks, they were a religious and military order that fought to defend the Holy Land, supposedly above war and petty politics. But in Europe they became entangled in local government, taking up positions as royal commanders, administrators and politicians. They led armies, attended Parliaments, and joined court intrigues and civil wars.

While the Knights Templar have long captured the public imagination, the Hospitallers were just as influential, yet their story has been left largely untold – until now. From the English invasion of Ireland through to Henry VIII's Dissolution of the Monasteries and beyond, the Hospitallers' story in Britain and Ireland sees the brethren drawn into civil wars, violent feuds, duels, assassinations and witchcraft.

Employing the latest research, Warrior Monks reveals the fascinating account of medieval Britain through the eyes of the Knights Hospitaller: a powerful order that made kings, toppled regimes and shaped history.