The King Behind the King by Warwick Deeping

In the forest there was an old stone quarry, and in the wall thereof some hermit of long ago had cut himself a little chamber; but the hermit had died in the time of the Barons' war, and the quarry was full of briers and brambles, broom and bracken. A tall beech wood shut it on every side, so that the place was like a pit into which sunlight fell only at noon and when the sun was high in summer.

In the doorway of this hermit's cell Fulk of the Forest sat on a truss of dead bracken, and stared moodily at the beech trees. His hands and feet were free enough, but the sides of the quarry went up like a castle wall, and Guy the Stallion and twenty men lay night and day among the bushes that half closed the entry. At night a large fire was lit, and he could hear those who kept guard laughing and singing, and telling lewd tales.