Lee Clayton

Lee Clayton was a companion of the Doctor. While the Judoon's scans identified him as human, the Thirteenth Doctor later assumed he had a bio-shield.

A faithful associate of the Doctor, he had received identical training to that of the Gallifreyan Gat, as demonstrated when Gat anticipated an escape trick of Lee's. He accompanied the Doctor while she hid on Earth in the early 21st century, in order to protect her while she became the unsuspecting human "Ruth Clayton" using a Chameleon Arch. He posed as her husband while they lived together in Gloucester. He was then seemingly executed by Gat, who had been hired to track down the "Ruth Clayton" Doctor and, at first, seemed to have mistakenly assumed that he was an incarnation of the Doctor. (TV: Fugitive of the Judoon)

Behind the scenes

 * Lee Clayton's species is not clarified in the episode, though there is certainly an implication that he is a Time Lord, if he shares Gat's training.