L is for... Lake, Jackson

 

When the Doctor visited London at Christmas, 1851, he was surprised to encounter another incarnation of himself who was battling the Cybermen. He had a companion named Rosita. The Doctor assumed that he was an incarnation from his future. Certain things did not add up, however. His sonic screwdriver was an ordinary wood and metal one - sonic only in that it made a noise when you hit it against something, and his TARDIS was a hot air balloon (Tethered Aerial Release Developed In Style). More tellingly, he only had one heart.

The Doctor discovered that he was holding the luggage of a man named Jackson Lake. It transpired that Lake had encountered the Cybermen in the cellar of his house, close to the Thames. They had killed his wife and abducted his son Frederic. They were using Infostamp devices to store data and one of these - full of information about their greatest enemy, the Doctor - had accidentally discharged itself into his mind. He had come to believe that he was the Doctor.

One he remembered who he was he joined forces with the Doctor to defeat the Cybermen and their human ally Miss Hartigan. They were using children like Lake's son as slave labour to build a Cyberking - a huge Cyberman craft / conversion unit.

After the threat had been eliminated, the Doctor using the balloon to get close to the Cyberking, he accepted an invite to Christmas dinner with Lake, Rosita and Frederic - something he generally declined.

Played by: David Morrissey. Appearances: The Next Doctor (2008).

• Morrissey and David Tennant had previously starred opposite each other in the musical drama Blackpool.
• He has recently starred in the Roman Britain series Britannia, and was the villainous "Governor" in the third and fourth seasons of The Walking Dead, as well as playing former British PM Gordon Brown.
• The episode title was chosen as Tennant had announced he was leaving the role, and the successor had not yet been made public. Morrissey was unable to tell his children about his character in case they divulged the information at school, causing them to be worried that they would be moving to Cardiff.