The Ballad of the White Horse by G. K. Chesterton
The story begins with description of the White Horse of the White Horse Vale and how it has seen untold ages pass by. Among these periods was the fall of the Roman Empire and the barbarian invasions that followed. The Danes have invaded and nearly conquered England, and now drive the Wessex King Alfred into hiding on the river island of Athelney. While there, the Virgin Mary appears to Alfred and gives him words of consolation. She does not promise him earthly victory, but reminds him of the promise of salvation.