Ambril was a Manussan historian. He served as the Director of Historical Research in 3426.
He took Lon and Tanha on a tour of the caves, where they met the Fifth Doctor. He believed the Mara had been destroyed, and disregarded the Doctor's warnings to the contrary.
Lon later took Ambril back to the caves and manipulated him into returning the Great Crystal to it's original place by threatening to destroy the priceless historical artifacts that were hidden in one of the caves. He and Lon returned to Ambril's office to inform Tanha that the Crystal would be returned during the ceremony.
He was later present when the Mara was destroyed by the Doctor. (TV: Snakedance)