Harriet Jones became Prime Minister of the United Kingdom as a result of winning a landslide majority in the 2006 election. (TV: The Christmas Invasion [+]Russell T Davies, Doctor Who Christmas special (BBC One, 2005).)
In an alternate timeline, the Albion Party won the United Kingdom election of 2046 under their leader Roger ap Gwilliam with a landslide majority of 96 seats. Ruby Sunday eventually aborted this timeline. (TV: 73 Yards [+]Russell T Davies, Doctor Who series 14 (BBC One and Disney+, 2024).)