An incarnation of the Doctor, and identified as such by the Thirteenth Doctor's sonic screwdriver, hid out on Earth using a Chameleon Arch, going by the name "Ruth Clayton". This Time Lord had a history working for Gallifrey, in a role "[one did not] apply for", which she sought, though failed, to abandon.
She had her TARDIS buried near the lighthouse where she stored her true identity, and trusted Lee Clayton to protect her, under cover as Ruth's husband. Lee was also tasked with reminding her to "Follow the light and break the glass" when the time was right, as this would lead Ruth to return to the lighthouse, which she was made to recall from childhood, and finally restore her Time Lord memories. (TV: Fugitive of the Judoon)
Biography
Working for the Time Lords
to be added
As Ruth Clayton
to be added