Previous Doctor

The Previous Doctor is the incarnation that immediately precedes the Riley!Doctor.

History
This incarnation of the Doctor, having learned of a divide between the Time Lords and the Sisterhood of Karn, opted to act on the information he had to try and repair the divide and stop Rassilon from achieving his ultimate goal. Believing that what he knew would make it impossible to stop him, however, the Doctor divised a plan, apparently at some point involving Roman. (The Handheld War) He opted to erase parts of his own memory, and prepare a Labyrinth where his memories would be returned and restored in his next incarnation. (Perfection)

Alternate versions
In another timeline, this version of the Doctor was captured and tortured by a version of Maxil who had become Emperor of Gallifrey. Our Doctor materialized in the torture chamber in the Capitol, replacing her previous incarnation, whose coat she recognized laying upon a table, and whose cane lay broken on the floor.

Behind the Scenes
The Previous Doctor is played by Joseph Scrimshaw, who appeared in the earliest versions of the live show at Gallifrey One. Scrimshaw has previously played as Peri and the First Doctor in these shows.