Bertrand Russell was a philosopher that the Fourth Doctor claimed to have met. (AUDIO: The Justice of Jalxar) The Eighth Doctor recalled a picnic in a dusty valley with Russell, Christopher Isherwood, Aldous Huxley and Greta Garbo. (PROSE: The Scarlet Empress)
Adric told Tegan that Principia Mathematica was by "a chap called Bert Russell". (TV: Four to Doomsday)
The First Doctor recalled that Russell had once said "something about the fact that the Earth’s sun having risen for countless millions of years being no guarantee that it would rise tomorrow." (PROSE: Galaxy Four)