The Second Doctor was portrayed by character actor Patrick Troughton.
The First Doctor may have had hearts of gold but he often came across as a stubborn and stern old man. The Second Doctor could not have been further from this picture… Overtly playful and eccentric he sometimes appeared to be a likeable but hapless buffoon. And yet his enemies often found out to their cost that this foolish facade concealed the keen mind of a genius!
During his second incarnation, the Doctor confronted familiar foes such as the Daleks and the Cybermen, as well as new enemies such as the Great Intelligence and the Ice Warriors. It was during this time that he first met Alistair Gordon Lethbridge-Stewart, in the tunnels of the London Underground. Following the defeat of the Great Intelligence, Lethbridge-Stewart was promoted to Brigadier and became the leader of the British contingent of UNIT, a military organisation tasked to investigate and defend the world from extraterrestrial threats. The Doctor reteamed with him to defeat an invasion of Cybermen in league with industrialist Tobias Vaughan.
The Second Doctor’s time came to an end when the TARDIS landed in the middle of a warzone, created by a race of alien warlords who, with the help of another renegade Time Lord the War Chief, progressively kidnapped and brainwashed humans into becoming soldiers for them, hoping to use the ones who survived to conquer the Galaxy. Although the Doctor was able to defeat their plan, he realised he would be unable to return the human subjects to their various original points in Earth’s history. He therefore contacted the Time Lords, sacrificing his own freedom in the process, and despite an attempt to escape was forced to return to his home planet. He was then put on trial by the Time Lords, for breaking their laws of non-interference. Despite the Doctor’s argument that the Time Lords should use their great powers to help others, he was sentenced to exile on 20th century Earth, the Time Lords forcing his regeneration into the Third Doctor in the process. Jamie and Zoe were returned to their own time, with their memories of all but their first encounter with the Doctor wiped and the secret of the TARDIS was also taken from the Doctor