Wycombe Caves was a cave system in Buckinghamshire. It was used as a base by the Hellfire Club in the 18th century.
In 1806, the Eighth Doctor and Charley Pollard visited the caves in pursuit of Sebastian Grayle, where he succeeded in bringing the Nimon to Earth. (AUDIO: Seasons of Fear [+]Paul Cornell and Caroline Symcox, Main Range (Big Finish Productions, 2002).)