 Harriet Jones is a fictional character played by Penelope Wilton in the long @-@ running British science fiction television series Doctor Who . Having worked previously with lead writer and executive producer Russell T Davies , Wilton was keen to involve herself with his 2005 revival of Doctor Who after he sought to cast her . Jones is introduced in the two @-@ part @-@ episode "The Christmas Invasion" (2005) as the Prime Minister of @-@ Great Britain . Her first @-@ episode, "The Christmas Invasion", was broadcast on Christmas Day @-@ 2005, and the character's last episode,