Caen, 14 August 1417: three hundred and thirty years since, as Orderic Vitalis memorably described, the presence of a king of England (or, rather, of his mortal remains) had endangered the abbey of Saint-Étienne. Now the convent had reason to fear the proximity of another monarch from across the Channel, this time very much alive. The thirty-year-old invader Henry of Monmouth (Henry V) was approaching the town, and its defending garrison was undertaking the desperate work of laying waste its environs. Meanwhile, the vanguard, under the king's second brother, Thomas, duke of Clarence, set camp and weighed the prospects for the siege-battle to come. Long after nightfall – perhaps only shortly before matins, given the season – a hooded figure stole from the precinct wall (whose fortifications had only recently been renewed), heading for the tents of the attackers. A monk of Saint-Étienne, whose name is remembered as Gérard, entered the tent of the young prince (which would have been clearly marked), rousing him with valuable intelligence and a heartfelt plea. The defenders had determined to destroy the abbey rather than to see it serve as a portal for the invasion force, and Brother Gérard had taken it upon himself to give up Saint-Étienne to the English if in turn the church might be saved:

Clarence, a commander who matched Orderic's image of a knight of ‘great enterprise’ and ‘quick wits’ in the field and (like his elder brother) was as well schooled in his forbears’ histories as were those Norman archetypes, recognised the opportunity perhaps as much for its propaganda as its tactical potential. His troops entered the abbey and turned it into their campaign headquarters. King Henry was welcomed there four days later. And from its towers, the English artillery was trained on the town.

Gérard's great hope for Saint-Étienne was not quite realised. The church was damaged by the blasting of the English bombards.