Justin of Wells

Sir Justin was a pious Christian knight from medieval England who was transported to the 20th century by the actions of the "demon" Melanicus, who briefly travelled with Fifth Doctor.

Biography
Melanicus, having seized control of the Event Synthesizer from the Prime Mover and using it to wreak havoc with time, caused Justin to be plucked from a joust in his own time. He collided with the Doctor's TARDIS outside of the usually peaceful English village of Stockbridge. The Doctor brought the unconscious Justin into the TARDIS, and when Justin recovered the Doctor was impressed with the ease with which he accepted his strange surroundings. Justin also believed the Doctor to be an angel of God, the TARDIS a miracle and their quest a crusade, despite the Doctor's attempts to disabuse him of the notion.

Justin accompanied the Doctor to the Time Lords' home, Gallifrey and the Althrace system to attend a meeting with the High Evolutionaries of Althrace who explained the situation. Eventually, with the help of Rassilon, Merlin the Wise, and Shayde, the Doctor was able to confront Melanicus, who had hidden the Event Synthesizer in a time-altered version of the local church. Justin, the Doctor and Shayde fought Melanicus. Justin gave the killing blow at the cost of his own life, all in a blinding flash.

With time set right, the Doctor regained consciousness in the restored church, now named St. Justinian's, in the 20th century, wondering if it had all been a dream. There, he saw a statue of Sir Justin, with an inscribed epitaph referring obliquely to his adventures in time and space. It was suggested that Merlin was responsible for the memorial. (DWM: The Tides of Time)