Exile on Earth
Following a trial by the Time Lords, Third Doctor spent some years as an exile on Earth. This is the main reason, along with Gallifrey's destruction in the time war, the Doctor is so defensive of the planet.
History
The trial
Following the defeat of the War Lord's allies, a triad of Time Lords tried the Doctor for violations of the Non-Intervention Policy. (DW: The War Games)
The Celestial Intervention Agency stepped in and appealed for a stay of execution. (DW: The Deadly Assassin)
The Time Lord tribunal said that they would try the Doctor two punishments:
- Exile on Earth during the late 20th century.
- A regeneration into a new incarnation, as too many people would recognize him on Earth.
(DW: The War Games)
- Neither of these sentences would follow immediately.
The Doctor as an agent
In reality, the Time Lords would not carry out their sentence immediately and the CIA would use the Doctor as their agent both with Lady Serena (PDA: World Game) and later with Jamie McCrimmon (DW: The Two Doctors).
- We do not know precisely when this period of the Doctor's life ended.
The Exile
The Second Doctor's exile
The Second Doctor spent most of his exile on Earth living the rich life at the Carlton Grange Hotel after spending many adventures with Jamie alone after The Two Doctors (Invasion of the Quarks to Martha the Mechanical Housemaid) and spending three adventures before this (Eskimo Joe to Operation Wurlitzer). This exile mainly features the Doctor's ambitions to rebel the Time Lords and be free once again. This exile consisted of TVC: Action in Exile through to U.F.O.. The Second Doctor's life ends in The Night Walkers when the Time Lords pass on the sentences and materialize the TARDIS somewhere else on Earth.
The passing of the sentences
The newly-regenerated Doctor's TARDIS eventually re-materialized in the Oxley Woods at the same time as an invasion by the Nestene Consciousness, in the late 20th century. An adventure followed, in which the Doctor helped UNIT defeat the Nestene Consciousness's Autons. The Doctor would stay on as UNIT's unpaid scientific advisor in exchange for a place to park the TARDIS and technical resources he needed to his ship. (DW:Spearhead from Space).
Bitterly resentful of his punishment, the Doctor suffered partial memory loss as a condition of his time travel, specifically as concerned the secrets of time travel (DW: The Claws of Axos.). He also did not remember all the materialization codes he needed to operate the TARDIS (DW: The Three Doctors).
Enter the Master
While based on 20th century Earth, a Time Lord appeared to warn the Doctor of the coming of the Master, an indirect way of sending him on a mission to defeat the Master's plots. (DW: Terror of the Autons).
The Time Lords allowed the Doctor to full use of his TARDIS to stop the Master, again, this time on an Earth colony in the future (DW: Colony in Space). Later, they allowed him to travel to Peladon for unspecified reasons (DW: The Curse of Peladon). Once, they even sent him on a direct mission to convey a message to Ky, a Solonian (DW: The Mutants).
- Almost certainly, the "Time Lords" in this instance meant the CIA.
The end of the exile
As a reward for defeating Omega, the Time Lords rescinded the Doctor's exile on Earth, granting him once more the freedom of space-time travel. (DW: The Three Doctors)
