Harriet Jones
Wilton returned for the series' 2005 Christmas special as Davies wanted to include a familiar character whose presence would ease the transition following a change in the series' lead actor. Despite her character having been introduced as fair-minded and hard-working, Harriet is depicted as an uncompromising Prime Minister, which led to comparisons to real-life politicians. Response to the character's political decisions prompted mixed commentary from the media; some reviewers felt that the character had acted unreasonably whilst others sympathised with her actions and felt her scripted political demise was unjust.
Wilton's last appearance in 2008 coincided with producer Phil Collinson's final episodes; she was keen to make a final return as she had been there for Collinson's first episodes as producer. Harriet is killed off in the penultimate episode of the show's fourth series in which she sacrifices her own life to help prevent a Dalek takeover of Earth. Harriet's final scenes were designed to complete a tripartite story arc and to give the character redemption. Provided by Wikipedia