Mark, Lord Haldoran was a tyrant who lived in England during the time after the 22nd century Dalek invasion and attempted to usurp the lands under his control of Lord London by force. This war was a necessary precondition of his eventual assumption of the English crown. He hoped to eventually be styled "Mark the First".
Sometime during the war, London gave his then-seventeen-year-old daughter Donna to Haldoran to marry in an attempt to create peace. Haldoran tortured Donna and constantly attempted to impregnate her, until it was discovered she was infertile. He divorced her and instead took her cousin, Brittany, and had twelve children with her. He warned Donna that if she ever returned, that he would make her life with him seem pleasant.
Sometime later in the war Lord Haldoran met a man named Estro, who offered Dalek guns in exchange for power in the conquered New London. "Estro" was actually the Master in disguise attempting to steal a Dalek weapon, and had created the war out of boredom. The Master supplied the weapons, but also began draining power from the base. When Haldoran inquired why this was happening, Estro claimed it was to power the new weapons. In truth, the Master was using the power to resurrect the Daleks.
He had extreme distrust with Barlow and Craddock, two generals who were important and loyal to him, yet he felt were too close. He ordered Tomlin to make them distrust each other. During a later battle, when Tomlin asked for reinforcements over radio, Haldorian told him that he was dying for him, and that was enough for battle.
Later, he encountered the Eighth Doctor, along with Donna and David Campbell. He kissed Donna, yet also drew in blood from her lip. He proceeded to try and shoot the Doctor, but he became distracted by Tomlin, who pointed a gun at him, calling him a traitor. He then shot Tomlin, informing him that it would have been better to shoot then to talk. Donna took his advice, and shot him in the face, killing him. (PROSE: Legacy of the Daleks)
The dictator's successor
After the death of the would-be "Mark I", Toby Barlow, who had been on his council, took his place. However, he did so by consolidating Domain Haldoran with Domain London and preferred to use the London title. As he told Brittany, "I'm none too fond of the title." (PROSE: Legacy of the Daleks)