Third Doctor (Exile)

The original third incarnation of the Doctor came into existence after her previous incarnation had committed suicide and changed gender. She arrived on Earth in 2003 and abandoned her TARDIS, all to hide effectively from the Time Lords.

Exile on Earth
After escaping the Time Lords, the Doctor fled to Earth. She took a job as a trolley stacker at Sainsbury's under the name "Susan Foreman" and spent her free time drinking copious amounts of alcohol with her workmates Cherrie and Cheese.

During some of her drinking binges she communicated with her previous incarnation, who chided her for her actions.

Capture and trial
Two Time Lords were sent to capture and return the Doctor to Gallifrey to stand trial. She eluded them on Earth for a time, but she ultimately found herself surrounded and too drunk to escape. She decided to come along quietly.

The Time Lords explained that her sentence was originally to be exiled to Earth, but since her escape had been such an embarrassment to all concerned, her sentence was elevated to death.

The Doctor was sent back to her TARDIS, to which she would be confined for the rest of her life. If she attempted to use the controls and escape, the TARDIS would dematerialise permanently, making it as though she had never existed.

Inside her TARDIS she found a note from one of the Time Lords who appeared to sympathise with her plight. It explained that her TARDIS was not rigged to self-destruct after all. She was being given a chance to escape whilst seemingly fulfilling her sentence. As she set the controls and the TARDIS began to dematerialise, she began to wonder whether the letter was truthful. (AUDIO: Exile)

The result was that her regeneration was undone - the Second Doctor, rather than committing suicide, stayed and accepted his sentence, although he was aware of the original timeline.