Jimmy Carter

Jimmy Carter was a President of the United States who, according to the Eighth Doctor, served in the 1970s and was succeeded by Ronald Reagan. (PROSE: Interference - Book One) His indirect successor from the 1990s, Tom Dering, once speculated that either he or Reagan must have secretly constructed Station Nine. (PROSE: Option Lock).

Carter's first name wasn't used in either Option Lock or Interference, but the common-sense interpretation of the two passages is that the authors were describing the real-life President Jimmy Carter.