Muldwych

Muldwych spent a thousand years stranded on Mount Kukúruk on Antýkhon. He assisted Bernice Summerfield and Ace with the Doctor's TARDIS. (PROSE: Birthright)

Muldwych gave the Seventh Doctor time rings for Bernice and Jason Kane's wedding. (PROSE: Happy Endings)

He was apparently a future incarnation of the Doctor.