Thomas Milligan worked for the NHS in 2008.
When the Saxon Master's paradox machine was destroyed, undoing The Year That Never Was and reversing time back to 2008, Martha Jones phoned doctor Thomas Milligan and then hung up, reassured that in the proper timeline he was alive. (TV: Last of the Time Lords)
When Martha was working for UNIT, and seconded to Torchwood 3 as a medical officer, she mentioned to the flirtatious Owen that she had a serious boyfriend who had once saved her life. (TV: Reset)
Martha later got engaged to Tom, who was a paediatrician working in Africa. (TV: The Sontaran Stratagem) Ultimately, however, Martha at some point later married Mickey Smith. (TV: The End of Time)
Alternate timeline
When the Master brought the Toclafane to Earth, Tom became a fugitive after the Great Decimation. (TV: Last of the Time Lords) At the end of The Year That Never Was, he first met Martha on a beach when she returned to England under the cover of night and was already familiar with her worldwide fame. (PROSE: The Story of Martha) He took her to see Professor Alison Docherty. When the Master tracked them down, he used his laser screwdriver to kill Tom. (TV: Last of he Time Lords)
Personality
In the Year That Never Was, Tom Milligan quickly took a liking to Martha Jones and proved to be very loyal to her. He even tried to attack the Master in an attempt to protect her, resulting in what would have been his death if time had not been reversed. Once the time line had been corrected, Martha sought him out. (TV: Last of the Time Lords) Although from his perspective he had never experienced the events of the Year That Never Was, he and Martha entered into a romantic relationship. They were also engaged at one point. (TV: The Sontaran Stratagem) However, Martha later married Mickey Smith. (TV: The End of Time)
Though he was a doctor, Tom would not hesitate to deal with matters through force, and kept a gun with him during the Year That Never Was. He killed one of the Toclafane after it said that killing humans was fun. He suggested using his gun to kill the Master, but Martha explained that Time Lords couldn't be killed so easily. (TV: Last of the Time Lords)
