The curator of the National Gallery in London was a mysterious individual who had insight into a particular Time Lord painting. He spoke with the Eleventh Doctor and told him that the name of the picture was in fact Gallifrey Falls No More, and pointed the Doctor in the direction of a search for Gallifrey.
The man then made some ambiguous references to possibly being the Doctor once, or that the Doctor was just a version of him. He states that he felt a desire to revisit old faces, but just a few favourites. (TV: The Day of the Doctor)