Third Assistant
From Tardis Wiki, the free Doctor Who reference
The Third Assistant was a person of the City who assisted Senta in performing life force extraction on the Savages. He helped perform the process on Nanina. He went to help the Second Assistant when he caught Dodo Chaplet trespassing in the laboratory.
He tried to prepare her for extraction but Dodo broke free and held him in a stand-off by threatening to destroy the laboratory equipment. (TV: The Savages)