Geffre lived on the planet on which Conrad was king. He and his friend Ernst were instrumental in helping the Second Doctor and Jamie McCrimmon organise a resistance group to overthrow Conrad's "evil" brother Gavin and put Conrad on the throne.
Ten years later, he and Ernst entertained the Doctor and Jamie when they "returned" to the planet. Since they had instead been on a doppelgänger planet, they needed information from Geffre and Ernst on what had happened to put Conrad on the throne. (PROSE: Twin Piques)