Joe Lynwood was came from an alternate timeline and was a homicide detective. One of his cases involved a strange set of murders involving time travel. He was hypnotised by Missy to be able to pilot Mark. He served in Iraq. He travelled in the TARDIS for 52 years.
An older version of him was interviewed for Dick Zodiac's America's Most Impossible Killers. He was concerned with Time Travel. This version told Mark of Missy's true identity. He created Dick Zodiac. (AUDIO: The Broken Clock)