Dr Joanne Porter, from Lincoln Castle, explained how the Chronica describes and illustrates a key moment in the battle: the death of rebel leader the Count of Perche.
“Unfortunately for him, a household knight actually manages to get his sword through the slit in his visor, so he meets an untimely end,” she said. “And of course that moment sends the rebel forces into disarray.”
Porter said she was delighted to have the book on display alongside the Magna Carta, from 1215, which was drafted just before the outbreak of the war, and the 1217 Charter of the Forest, which was part of the peace negotiations.
“It depicts such a pivotal moment in English history that happened basically right here,” she added.
The Chronica Majora is on display in the David PJ Ross Magna Carta Vault at the castle.