Ian Chesterton was one of Susan Foreman's teachers at Coal Hill School, London. He was intrigued by her advanced scientific knowledge, and in talking with another of her teachers, Barbara Wright, found that he was not the only person who had noticed the strange knowledge of this pupil. One evening, as school was finishing, Ian and Barbara decided to follow Susan home. They were concerned about her, and curious. When they saw Susan enter I.M. Foreman's junkyard in Totter's Lane, the two school teachers became more concerned for her safety. Following her inside the yard, the two discovered a police box sitting incongruously among the junk. When they discovered that Susan was inside, they barged their way in and Ian discovered something he could not believe.
Ian provides the series with an action-oriented figure, able to perform the physical tasks that the elderly Doctor can not. His concern, above all, is for the safety of the TARDIS crew, and in the early stories he often takes issue with the Doctor's habit of placing the group in harm's way just to satisfy his own curiosity. The chemistry between Barbara and himself is also evident, although the nature of their relationship is never made explicit in the television series.
Ian shows a surprising breadth of skills throughout his tenure with the Doctor. He manages to create fire, rides a horse, knows how to fight with swords and is knowledgeable about pressure points that can paralyze an opponent. He is also fiercely protective of Barbara, going on a lone mission to rescue her from Saracens in The Crusade. In that story, he is also knighted by King Richard I of England as "Sir Ian of Jaffa". After many travels, Ian and Barbara eventually use a Dalek time machine to get home, albeit two years after their disappearance.
