Jeremy Thorpe

From Tardis Wiki, the free Doctor Who reference

Jeremy was the first name of the British Prime Minister with whom the Brigadier conversed on the phone. (DW: The Green Death)

He probably succeeded Edward Heath.

Behind the Scenes

The Doctor Who production team, operating on the assumption that the UNIT stories took place in the near future intended (not entirely seriously) the reference a suggestion that Jeremy Thorpe would get elected as Prime Minister. This did not happen in reality.