Harriet Jones (Pete's World)
From Tardis Wiki, the free Doctor Who reference
For the real-world individual, see Harriet Jones
While Harriet Jones became Prime Minister in 2006, her duplicate in Pete's World became President of Great Britain around 2007. It is unknown how long she stayed in office or when she died. The Doctor did not know there was a parallel version of his old friend until Pete Tyler told him that she had replaced the previous President, to which the Doctor replies "keep an eye on that one." (DW: Doomsday)
