Jackson LakePortrayed by: David Morrissey
Travelled with: Tenth Doctor
Appearances: The Next Doctor (2008 Christmas Special)
Associated with: N/A
Enemies encountered: Mercy Hartigan, Cybermen
Jackson Lake first appeared in The Next Doctor (2008 Christmas Special) as a man who believed himself to be an incarnation of the Time Lord, the Doctor. Jackson was a former mathematics teacher who moved to London in 1851 with his wife, Caroline, and son, Frederick. Here, they encountered Cybermen, who killed his wife and abducted Frederick. Jackson defended himself by using one of the Cybermens infostamps, but the device backfired and filled his mind with information on the Doctor that the Cybermen had. In his anguish over the loss of his family, Jackson's mind fooled itself into believing that he was the Doctor, newly regenerated and amnesiac due to the Cybermen attack. Sometime after this, Jackson rescued a woman called Rosita, dubbing her his companion the duo began to work on his TARDIS – the Tethered Aerial Release Developed In Style. Assuming the Doctor's identity, Jackson continued to act as the Doctor would, investigating the disappearance of several local children, as well as the man named Jackson Lake. Soon, his exploits brought him into contact with the real Doctor, who believed Jackson to be a future incarnation, though quickly began to suspect that he wasn't. After collecting evidence, the Doctor deduced Jackson's real identity and revealed it to him, though this caused Jackson to have a breakdown, discovering who he really was. Jackson told Rosita to accompany the Doctor while he went to confront Mercy Hartigan. Jackson was able to recover most of his memory, but was unable to recall what the Cybermen took from him. As he tried, he found the courage to join the Doctor and Rosita, arming himself with a bandoleer full of infostamps. Jackson used the devices to attack the Cybermen, helping the Doctor and Rosita fight their way under the River Thames, where the kidnapped children were being used as slave labour. As the Doctor and Rosita began to evacuate the children, Jackson remembered that the Cybermen had taken his son, whom he found in the factory. But Jackson became paralysed with fear and was unable to save him, but marvelled at the Doctor who leapt into action and rescued Frederick. From the streets, Jackson then watched the Doctor stop the Cyberking and end the Cybermen threat. However, his shared memories with the Doctor made him see that the Doctor was rarely thanked for his efforts, so Jackson rallied the assembled masses to cheer for and thank the Doctor. Jackson met the Doctor by the real TARDIS, though now a widower with a young son, Jackson wasn't going to join the TARDIS crew, though he was allowed to see inside the TARDIS. Overcome by the unbelievable, Jackson forced himself to exit before inviting the Doctor to a Christmas dinner after appointing Rosita as Frederick's nanny. The Doctor declined at first, but then accepted when Jackson suggested it be "in honour of those we have lost."
Before the Cybermen invasion, Jackson was an average, shy man, however due to the effect of the infostamp and acting under the belief that he was the Doctor; Jackson became a brave, dashing hero. His confidence waned when his memories as Jackson Lake returned, but the Cyber threat uncovered a true bravery deep within himself, which the Doctor said was his own doing and nothing to do with the infostamp. Even after Jackson's real memories returned, he still retained much of the knowledge he had obtained of the Doctor, though he still found it hard to accept the reality of the real TARDIS. While acting as the Doctor, Jackson carried his own version of a Sonic Screwdriver that turned out to be just a normal screwdriver. He also carried a fob watch, which the Doctor considered might be a Chameleon Arch fob watch, but it had a normal clock face, though it did help reveal Jackson's identity, as his initials were engraved on the back.