Teel was a Dulcian who was a student of Educator Balan. He led an academic field trip to an island used in the past for atomic testing. While there, he encountered the Second Doctor, Jamie, and Zoe after the TARDIS materialised on that island on Dulkis.
He, Kando, Zoe and Balan were forced by the Dominators to clear rubble from a drilling area. They were rescued by Jamie and Cully. (TV: The Dominators)