Calagundus (The Prodigal Sun)

When  was eleven, he followed the druid Cunovellasus as he left the clan to prepare for the winter solstice.

At the ruined temple, they encountered the Fourth Doctor and Leela, who helped them scare off the shadow-men who were approaching.

Afterwards, Calagundus suggested the Doctor and Leela join them for their clan's festivities. (PROSE: The Prodigal Sun)