Sir Justin of Wells (AUDIO: Castle of Fear) was a pious Christian knight from medieval England who was transported to the 20th century by the actions of the "demon" Melanicus. He travelled briefly with the Fifth Doctor.
Melanicus, having seized control of the Event Synthesizer from the Prime Mover and used it to wreak havoc on time, caused Justin to be plucked from a joust in his own time. He collided with the Doctor's TARDIS outside the usually peaceful English village of Stockbridge. The Doctor brought the unconscious Justin into the TARDIS. 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 confronted 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. (COMIC: The Tides of Time)
Behind the scenes
"Justin of Wells" was not the formal name by which Justin was knighted, since when he met the Doctor he claimed to "have no fief". Nyssa may have made up the name, or she may have been using a name awarded him after death. In any case, the name is logical, since Justin met the Doctor in Wells Wood.