Timothy Dean was a student at Hulton College in 1914. He was often picked on by other students due to his smaller frame. He accidentally found the pod where the Seventh Doctor had stored his biodata while living as the human John Smith.
Leakage from the pod began to give Dean Time Lord abilities. When one of his classmates hanged him, the respiratory bypass system he had developed saved his life.
When the Aubertides came looking for the pod, Dean was able to convince John Smith to become the Doctor again. Afterward, he lived a long life. Though fully human, Dean retained the best parts of the Doctor.
An objector to war, he volunteered to join the Red Cross during World War I. When he was stationed in the Somme in July 1916, he saved the life of Captain Richard Hadleman, whom he recognised from his time at Hulton College.
During his old age, he continued to attend annual remembrance services to the war in Norwich Cathedral, wearing a white poppy. He died in 1995. (PROSE: Human Nature)
Behind the scenes
Timothy Dean was the basis, in part, for the character Tim Latimer in Human Nature / The Family of Blood. Both the novel and the TV story were written by Paul Cornell.