Jackie Lane
Jackie Lane (born 10th July 1947 in Manchester) played Dodo Chaplet, one of the Doctor's companions, from the conclusion of "The Massacre of St Bartholomew's Eve" to "The War Machines." She played the part from February to July 1966 alongside William Hartnell as the Doctor.
Lane was 18 when she played the role and thus was the youngest female actor to have played a companion in the series — Matthew Waterhouse, who played Adric in the early 1980s, being the youngest male actor to have played a companion. She went on to become a theatrical agent, representing Tom Baker, who would play the Fourth Doctor in 1974 and Janet Fielding, who would play companion Tegan Jovanka in 1981.