Siege of Couronne

In the year XI, 255, when the Bretonnian city of Couronne came under siege by a great warherd of Beastmen, aid unlooked-for arrived in the form of a High Elf army under the command of Imrik of Caledor. In truth, the High Elves cared not for the fate of the Bretonnian city -- their only concern was the sanctity of the waystones that now lay buried beneath Couronne's chief castle. So it was that Dragon Princes battled snarling Gors alongside Knights of the Realm; that the shieldwalls of stocky Men-at-Arms were flanked by regiments of noble High Elf archers and stern Phoenix Guard.

In Bretonnia, bards tell that Prince Imrik and King Charlen fought like brothers that day, fighting as one against every foul Jabberslythe and Ghorgon to emerge from the Beastmen's ragged ranks. A few even claim that King Charlen saved Imrik's life, spearing the Cygor that had swept the Elf from his saddle before it could stomp him flat. For their part, the Elves remember the Bretonnians as crude but enthusiastic fighters, whose valour almost overshadowed their impertinence. Prince Imrik never forgave Charlen for stealing a good many of his kills.

Source
pg. 32
 * Warhammer Armies: High Elves (8th Edition)