The Little Gentleman, by Phillippa Pearce, 2004

Bet doesn't know why Mr. Franklin has asked her to read a scientific book about worms while sitting on a log in a meadow, but she doesn't mind doing it anyway. Mr. Franklin isn't cracked in the head after all, she learns, when a mole pops his snout out of his hole and starts speaking with her about earthworms, Mr. Franklin, and the failed Jacobite plot of 1702 to place James of Scotland on the British throne. Contemporary fiction meets history by way of an underground twist, and "the little gentleman in the velvet coat" whose hole caused King William's horse to trip, comes to life in modernity and tells his story. A delicate hand makes this extraordinary premise believable and delightful. Recommended.