Dr Charles Percival, (TV: The Time Monster) also called Charles Perceval or, rarely, Humphrey Perceval, (PROSE: The Time Monster) was the director of the Newton Institute at the time that the Master was working on TOMTIT. The Master hypnotised him when he questioned his credentials.
He helped lure Sergeant Benton away from the Master's laboratory so the Master could summon Kronos. Percival was later killed by Kronos. (TV: The Time Monster)