At the Academy, Mortimus was a friend of the Doctor's, and a member of a cabal of ten rebellious young Gallifreyans at the Academy known as the Deca.
Mortimus was the owner of a Mark IV TARDIS and said that he had left the Doctor's home planet some fifty years after the Doctor.
He decided that he liked to meddle with history, specifically the history of Earth, and to change it for his own amusement and for what he considered to be the better. He leant mechanical assistance to the builders of Stonehenge and gave Leonardo da Vinci tips on aircraft design. At the time that the Doctor, encountered him, the Monk attempted to prevent the Norman Conquest of 1066 as part of a plan to guide England into an age of technological prosperity. On that occasion he wore the guise of a monk in order to gain the trust of the locals, hence the name by which he is most often referred.
The Monk was at this time a well-meaning but childish man who was not half as clever as he thought he was, and who never seemed to realise the seriousness of what he was doing. The Doctor sabotaged the dimensional circuit of Mortimus' TARDIS, making it the same size inside as outside, reducing the interior to dollhouse proportions.
Next Encounter with The DoctorEdit
The Doctor encountered him again on the volcanic planet Tigus, where Mortimus sabotaged the lock on The Doctor's TARDIS, though that did not stop him from getting inside. The Doctor stole Mortimus' direction controls in order that he could use it himself as part of his effort to stop the Daleks.
Mortimus' TARDIS landed in ancient Egypt. Having heard of the Daleks, the Monk went along with their plans, in order to avoid being exterminated himself, while trying without success to convince the Doctor and his companions of his honourable nature. While there, the Doctor tinkered with the chameleon circuit from Mortimus' TARDIS, making it assume various shapes, finally that of a police box. He stole its partially compatible directional unit, leaving Mortimus stranded in a cold, icy location planet.
Ally of the Ice WarriorsEdit
Mortimus then teamed up with the Ice Warriors and battled the Doctor in a complex scheme involving alternative Earths and a plan to build a giant sonic weapon. Mortimus now preferred his own TARDIS to appear as a police box, did not wear a monk's habit, and referred to himself as the Time Meddler.
The Sleeze BrothersEdit
At some point in the 21st century, the Monk tried to rig elections in what might have been the United States to stop President Sintatra from winning a third term of office. As he began this mission, he landed his TARDIS on a busy freeway. The Sleeze Brothers, El Ape and Deadbeat, collided into it, causing significant damage to their vehicle. At the same time, the companion-less Doctor landed his TARDIS in the same area.
Besieged by both angry brothers and an irate Doctor, the Monk slipped back into his TARDIS and took off. The Brothers then hijacked the Doctor's TARDIS at gunpoint and ordered him to follow the Monk's TARDIS through time. A chase ensued, and the two TARDISes flitted through time to several famous mysteries in Earth's history. Eventually, the Doctor and the Sleeze Brothers caused the Monk's TARDIS to implode, which apparently caused the creation of the Bermuda Triangle. How, when, or if the Monk reconstituted his TARDIS wasn't clear.
At some point, the Monk regenerated at least once. Therefore, when they next met, the Doctor did not recognize him by sight.
Mortimus then created a series of alternate timelines in a scheme employing the Chronovore Artemis. Mortimus now used his real name and posed as a 1976 record executive in England. He had also, at this time, served as the Champion of the Eternal Death in the same way that the Doctor served as Champion of Time. In so doing, he had made himself servant to a being much more powerful and intelligent than himself. Mortimus aided the Vardans' scheme to avenge themselves on the Doctor and the Sontarans by conquering Earth, a planet of continued strategic value to the Sontarans and obviously important to the Doctor. His plan was undone thanks to the Doctor's companion Ace, who pretended to side with him until she could free Artemis. The vengeful Artemis subsequently took Mortimus away to make him pay for her imprisonment.