Ian Chesterton played by William Russell (Russell Enoch)
Ian was a science teacher at the Coal Hill school. Eager to find out more about Susan's advanced knowledge he and Barbara Wright followed Susan back to Totter's Lane. He followed Barbara after she barged into the TARDIS after Susan.
Being a science teacher Ian was able fascinated by the technology of the TARDIS, although when the Daleks' time machine became available he and Barbara were able to return to their own time.