The most famous bloodthirsty tyrant in literary history was, in reality, a generous, golden-haired, highly successful king who ruled for 17 years and peacefully went on pilgrimage to Rome. The historical Macbeth is the ultimate case of whiplash, a competent statesman whose entire legacy was erased because a playwright needed to flatter his royal patron.

This episode reconstructs Macbethad mac Findlaich, King of Alba from 1040 to 1057, from surviving 11th-century sources. We strip away 400 years of theatrical myth to examine how he really took the throne, what his prosperous reign looked like, and the step-by-step mechanics by which Shakespeare transformed a respected ruler into pop culture's blueprint for evil ambition.

• The name Macbethad means son of life and signals piety, not a patronymic; his actual father-name was mac Findla ...