Susan Foreman (Carole Anne Ford)
Apparently the Doctor's 15 year-old granddaughter, Susan was attending school in England when two of her teachers, Ian Chesterton and Barbara Wright, intrigued by her unusual intelligence, investigated her mysterious home life. This forced the Doctor to whisk them away on a series of journeys, rather than allow them to reveal what they had discovered.
Susan was fiercely loyal to the Doctor, and developed a close bond with Barbara. Her adventures in history included encounters with Marco Polo, the Aztecs and Napoleon. After the Doctor had defeated the Daleks' attempt to invade Earth, he left Susan behind, knowing her future was with young freedom fighter David Campbell.