Abigail Holt was the pseudonym of a girlfriend of Benjamin Franklin in 1762, whilst he was staying in London.
She was an aristocrat and relative of the King. Holt was married but lived apart from her husband under the name Abigail Holt. She told her real name to Steven Taylor but he did not or did not want to remember it.
Her appearance did not match her position completely, leading the First Doctor, Steven and Vicki to a suspicion that she was a time traveller herself and wanted to change the history. This suspicion turned out to be unfounded.
She loved Franklin, and he was attracted to her love of science and politics, about which they engaged in discussions at the Pennsylvania Coffee Shop. However, as Franklin had a wife in America, he was wary about their relationship being public. Benjamin's son, William Franklin, knew about their relationship. Vicki noted that he did not approve of it and saw that as a bad omen for their future.
At the time, Benjamin Franklin was involved in a legal dispute with the Penn family, including Thomas Penn. When Holt's relationship with Franklin was discovered by the Penns, they blackmailed her into spying on Franklin threatening to reveal her affair to her husband otherwise. She could not hide anything from her lover, so Franklin supplied her with information to relay to the Penns. According to her, she did not have to lie as he had nothing to hide.
Although the history forgot her, the Doctor thought that she and her treatment by the Penns had a profound influence on Franklin. The copy of the Doctor's mind considered her unimportant. Steven demonstrated this discrepancy to persuade his granddaughter Sida that the copy cannot be compared to the real Doctor. (AUDIO: The Founding Fathers)