H is for... Hobbes

Professor Winfold Hobbes regarded himself as an expert on the planet Midnight, whose surface was bombarded by lethal X-tonic radiation which meant no life could possibly exist there. Hobbes was one of the passengers on the heavily shielded Crusader 50 tour of the planet which the Tenth Doctor took. This was Hobbes' fourteenth such trip. He was accompanied by one of his students, Dee Dee Blasco. After the Doctor had sabotaged the in-flight entertainment system, and encouraged the passengers to talk to each other, Hobbes delivered an impromptu lecture on Midnight. However, once the Crusader vehicle came under attack from an invisible entity, which could take over people's bodies, Hobbes became sucked into the mounting paranoia of the tour group - causing him to turn on Dee Dee and to agree to throw the Doctor out of the vehicle when it appeared that the entity had taken him over. When the crisis was over, he was left ashamed of his actions.

Played by: David Troughton. Appearances: Midnight (2008).

• David Troughton is, of course, the son of Patrick Troughton, the Second Doctor. He appeared in the series during his father's tenure - first in a minor extra role as a guard in The Enemy of the World, and then in the more substantial role of Private Moor in The War Games. He returned to the series during Jon Pertwee's time as the Doctor, to play King Peladon in The Curse of Peladon. He was sharing digs with future Doctor Colin Baker at this time.
• Before Paul McGann became the Eighth Doctor, Virgin Books had planned to regenerate the Seventh Doctor in their 'New Adventures' range, and approached Troughton to use his image as their new Doctor.
• Troughton only stepped into the role of Prof. Hobbes at the last minute, after the actor who was to play him - 'Allo 'Allo's Sam Kelly - broke his leg.