1 of 12 Billie Piper is to follow in a long line of actors who have travelled through time with Doctor Who - including two early assistants Vicki, played by Maureen O'Brien, and Steven Taylor (right), played by future Blue Peter presenter Peter Purves.
2 of 12 Another companion was Jamie McCrimmon, played by Frazer Hines - who went on to star in soap opera Emmerdale. Jamie was rescued from the battle of Culloden in 1746 by the second doctor, Patrick Troughton.
3 of 12 Deborah Watling starred as Victoria Waterfield, who also travelled with Troughton. The daughter of a Victorian scientist, she became orphaned when the Daleks killed her father.
4 of 12 A librarian who was attacked by the Cybermen, Zoe Herriot, played by Wendy Padbury, was highly intelligent but inexperienced.
5 of 12 The Brigadier (Nicholas Courtney, centre) headed the United Nations Intelligence Taskforce, while Jo Grant (Katy Manning) trained as a spy and was assigned to UNIT.
6 of 12 Sarah Jane Smith, played by Elisabeth Sladen, was the journalistic sidekick to third doctor, Jon Pertwee.
7 of 12 Leela (Louise Jameson) was a tribal warrior leader who joined up with the Doctor, Tom Baker, because he looked like their god.
8 of 12 One of the Doctor's most famous companions was a robotic dog, K9, which travelled with Romana II (Lalla Ward).
9 of 12 An air hostess, Tegan Jovanka (Janet Fielding), joined Peter Davison after thinking the Tardis was a real police box.
10 of 12 Nicola Bryant played Perpugilliam "Peri" Brown, who joined Davison as an 18-year-old American botany student.
11 of 12 High-pitched dancer Bonnie Langford travelled with both Colin Baker and Sylvester McCoy (pictured).
12 of 12 The Doctor's last regular companion was Ace, played by children's TV presenter Sophie Aldred.