Saxon Master

Harold Saxon was an alias and identity adopted by the Master when he passed himself off as a Human politician.

Regeneration
Recently liberated from the Human form of Professor Yana, he fatally wounded his assistant, Chantho, who though dying, fired a gun at him. The wounded Master managed to get into the Doctor's TARDIS. He decided that since the Doctor had a youthful new body, he could too and so regenerated into one. The Master then left the Doctor on the planet Malcassairo with Futurekind about to burst in the laboratory door. The Master now had the TARDIS and the Doctor's hand, which Jack Harkness had taken with him to Malcassairo, that contained the Doctor's DNA. (DW: Utopia) He took the stolen TARDIS to Earth in the 2000s, about one and a half years before the Doctor had even met his current companion Martha Jones. (DW: The Sound of Drums)

Political career
On Earth, the Master began to fabricate a past for himself. As a politician, the Master used the simple slogan "Vote Saxon" (TW: Captain Jack Harkness) He was active from at least as early as 2007, when he started campaigning for the general election as Prime Minister of Great Britain (DW: Love & Monsters). By Christmas of 2007 he had enough authority to order the British Army to use tanks to fire at and destroy the Empress of the Racnoss's webstar. (DW: The Runaway Bride)"Saxon" asserted that extraterrestrial life did exist and that the British must do something about the fact. This stance made him popular in early 2008 after reports from the Judoon having transported the Royal Hope Hospital to the Moon (DW: Smith and Jones)

Technological innovations
The Master started the Archangel Network. This telecommunications network, tied to mobile phones, carried a subtle mind control signal which made Humans trust him. The network affected the Doctor so that, on Earth earlier, he had never had any suspicions as to "Saxon". To those few Humans conscious of it, the signal sounded the persistent drumbeat (the same as the constant drumbeat the Master always heard) that only they could hear.

He also designed the Valiant, UNIT's air carrier as well as a laser screwdriver, which he reserved for his own use. (DW: The Sound of Drums) "Saxon" funded the rejuvenation experiments of Richard Lazarus. (DW: The Lazarus Experiment) With the results from this, as well as the Doctor's DNA, the Master learned how to apply the results to the laser screwdriver, in order to age the Doctor.

Other activities
The Master also contacted the Toclafane, the child-like yet vicious cyborg remnants of the future Humans who had never found Utopia. (DW: The Sound of Drums) He also cannibalized and converted the Doctor's TARDIS into a paradox machine so as to change history. (DW: The Sound of Drums / Last of the Time Lords) At some point he also took a devoted Human wife, Lucy. (DW: The Sound of Drums) After Martha had left with the Doctor, he had an agent meet with Martha's mother Francine and tap into a conversation between Francine and Martha via the superphone, which could contact Martha through space and time. (DW: 42)

As Prime Minister
In 2008, he was elected as Prime Minister. He gassed to death his cabinet in the recently rebuilt 10 Downing Street and shortly afterward announced first contact with the "friendly" Toclafane who could protect Earth against alien threats. He put Jack Harkness's allies, Torchwood 3 on a futile trip to find him in the Himalayas and branded the Doctor, Jack and Martha as criminals. The Master repaired to The Valiant, which the governments of Earth considered neutral territory and therefore fitting for formal first contact with alien life, the Master had the Toclafane murder the American President Elect Arthur Coleman Winters. The Master captured the Doctor and Jack Harkness, who had come to The Valiant. Earlier that day, the Master's agent had had Francine Jones, Martha's sister Tish and her father, Clive arrested and taken to the Valiant. (Martha's brother Leo had received a warning from her and gotten away in time.) (DW: The Sound of Drums)

During The Year That Never Was
The Master used his laser screwdriver to kill Jack and to age the Doctor about a hundred years. Martha managed to escape. The Master ordered the Toclafane to kill one tenth of humanity and commenced their invasion (DW: The Sound of Drums ). One year later, in 2009, the Master had converted Earth into a slave camp which he ruled from The Valiant. Here the Master kept Martha's family, the Doctor, and Jack imprisoned. The Master hoped to soon expand his New Time Lord Empire into space. Martha used the legend of the Doctor, which she had spread, and the thoughts of Earth thinking "Doctor" at the same time, channeled their psychic energy through the Archangel Network, which the Doctor had spent a year infiltrating with telepathy. The psychic energy restored the Doctor and give him telekinetic powers. Jack attacked the paradox machine and reversed time back one year. (This wouldn't affect anyone aboard The Valiant.) Lucy shot her husband, who, defeated, refused to regenerate. The Master then died in the Doctor's arms.

An unknown woman, however, stole the Master's ring, with a Gallifreyan insignia, from his funeral pyre. The identity of the person and significance of this action, if any, remains unclear. (DW: Last of the Time Lords)

Personality
"Saxon"'s nature bordered on and even overlapping utter insanity. Usually in a disturbingly happy mood, he grinned manically at the slightest occurrence, and often did strange and unpredictable things. Such examples include repeatedly opening a door to look at the Toclafane murdering a reporter, giving a thumbs up to a man choking on gas, and childishly chiding the Doctor. He did have a dark side though, where he becomes rather serious with just a touch of malicious humour. He took pleasure in the death and suffering of others, and was extremely manipulative.

Behind the Scenes
The first, very minor reference to Harold Saxon, occurs in Love & Monsters when the Abzorbaloff sits reading a paper which mentions a Saxon election victory on its cover. The second, and first, direct reference happened in a dialogue reference at the end of The Runaway Bride.

The BBC created an official in-universe campaign website for the election as well. In 2007, a popular online meme among Doctor Who fans making the popular the "Vote Saxon!" slogan.