A young Benedictine monk named Eilmer launched himself from Malmesbury Abbey's 150-foot tower in the early 1100s, wearing wings crafted from willow wood and cloth. He glided roughly 600 feet before crash-landing near the river Avon, breaking both legs. The abbey commemorates this aviation experiment with a stained-glass window.

The account comes from historian William of Malmesbury, writing around 1125, who noted Eilmer's later comment about seeing Halley's comet in 1066: "It is long since I saw you." This sparked debate among scholars about whether Eilmer witnessed the comet twice - once as a child in 989 and again in 1066.

University of Leicester researcher James Aitcheson challenges this theory in Notes and Queries, arguing Eilmer likely saw a different comet in 1018. This would push his birth date significantly later and place his famous flight attempt in the 1020s-1040s timeframe instead. The dating hinges on whether he was actually referring to Halley's comet or another celestial event.

The mystery highlights how historical records blur the line between legend and fact. Without precise dates, Eilmer's aerial ambitions remain compelling folklore rather than verified medieval engineering.