Marcus Aurelius Gallius

 was a Centurion leader of the Roman Empire from 60 AD who encountered the Ninth Doctor after being displaced in time by a time eddy into 1959 London.

Marcus was due to attack the army of Boudica at Colchester before his century was captured by one of Audrey Mohinson's time eddies, leading his terrified men to kill over 300 innocent civilians. Although the Doctor attempted to reason with him while on the trail of the eddies, it did not work and he ordered his soldiers to attack Captain Halloran and Lieutenant Farraday. (AUDIO: Sphere of Freedom)

When the Doctor, Nova and Farraday accidentally landed back in London and recovered Marcus and Halloran, Marcus refused to accept help and tried to attack his saviours, leading the Doctor to show him the Time Vortex first hand, convincing him to work with them to stop Audrey and the Ravagers. When the Doctor was imprisoned on the Sphere of Freedom, Marcus used strategy to create a diversion so Nova could activate a group of drones and destroy the time particles, but doing so caused a time eddy to capture the Doctor. Marcus was forced to watch as the Ravagers started destroying the universe.

When the Doctor changed the timeline to stop the Ravagers for good at an earlier point in time, the retroactive fixes to time meant that none of the events of being transported to the twentieth century ever happened. (AUDIO: Food Fight)