Gary Russell (in-universe)

Gary Russell was a historian who helmed the effort to translate the fragments of the Scrolls of Gallifrey inexplicably found in a churchyard in Berkshire. (PROSE: The Legacy of Gallifrey)

Behind the scenes
This Gary Russell is ostensibly named for the real-life author of the short story The Legacy of Gallifrey.

An in-universe Gary Russell was also be mentioned in a brief skit created in 2018 by David and Georgia Tennant as a gift to the real-life Russell, with Georgia later posting the skit on Twitter. The scene had the Tenth Doctor reveal to Jenny that Gary Russell was a fixed point in time, leading him to panic when he realised that Russell had vanished from Cardiff; however, the Doctor's fears that the Cardiff Space-Time Rift is involved then prove unfounded, as Russell, just like his real-life counterpart on the occasion when he was gifted the skit, was simply going on holiday to Australia.