The comet bearing Edmond Halley's name may have been misnamed! New research from Leiden University reveals that an 11th Century English monk recognised the famous comet's periodicity centuries before the British astronomer. Eilmer of Malmesbury witnessed the comet's appearances in both 989 and 1066, linking the two observations and understanding they represented the same celestial visitor returning after decades, a realisation documented by the medieval chronicler William of Malmesbury but overlooked by scholars until now. The discovery challenges whether history's most famous comet should continue bearing Halley's name when a Benedictine monk beat him to the discovery by more than 600 years.