For nearly 900 years, the sudden death of King Henry I of England has been attributed to accidental poisoning after dining on a large dish of lampreys, one of the ugliest fish on the planet.

But now a US-based doctor has challenged this centuries-old diagnosis and claimed the British monarch most likely died of acute meningitis secondary to Listeria monocytogenes.

The king — who was in his late 60s at the time — famously retained the “tremendous energy” of his youth until his fatal illness, writes Dr Matthew Turner from the Madigan Army Medical Center near Lakewood, Washington.

On 25 November, 1135, Henry had spent a long day hunting in the forest of Lyons in France and, upon returning to his lodge at Lyons-la-Forêt, had ordered his huntsmen to prepare for another hunt the following day.