A Knight from an alternative universe where magic lives side by side with technology. In this domain, he knew the Doctor as the wizard Merlin. When Queen Morgaine travelled to our universe to seek King Arthur, Ancelyn followed to stop her from obtaining the sword Excalibur. Ancelyn joined forces with the Doctor and UNIT Brigadier Bambera to fight Morgaine and her son Mordred. After they had been defeated, Ancelyn stayed on in this universe, as he had taken a shine to Bambera.
- Ancelyn's name derives from Lancelot, the Arthurian Knight.
Played by Marcus Gilbert. Appearances: Battlefield (1989).