Unbound Doctor

An incarnation of the Doctor in an alternate universe was exiled by the Time Lords of that dimension at the end of his second incarnation. Instead of being exiled to the 1980s, he was sent to the late 1990s. Because of this, the Doctor was not present to help UNIT where in the prime universe the Third Doctor did.

He could speak Mandarin, Cantonese, Manchu, Mongolian and Hokkien.

To the Chinese, he was known as Hu (the Tiger, for his courage), Hu (the Fox for his cunning) and Xue (Doctor, he who tends to the sick). The last of these was his personal favourite. (AUDIO: Sympathy for the Devil)

History
After being put on trial by the Time Lords, the Doctor was told that he would be exiled to Earth in the 1980s. However, he was instead sent to Hong Kong on 30 June 1997.

Immediately after leaving the TARDIS, the Doctor bumped into Marcus and Adam. He followed them to the Little England, a pub run by Aistair Gordon Lethbridge-Stewart. The Doctor recognised the Brigadier and convinced him that he was the same person who he fought Robot Yeti with in the London Underground.

During their conversation, a Chinese plane disguised with chameleon circuit technology flew over them and crashed onto a nearby mountain. The Doctor and the Brigadier went to the crash site and helped the pilot get out of the wreckage and recover. UNIT arrived and brought the pilot to a nearby monastery. At the monastery, the Doctor heard that Ling saw a man change his appearance and realised that the Master was on the crashed plane.

The Master revealed himself by releasing an alien parasite which had been kept trapped at the monastery. The Doctor talked with the Master and made a deal. The Master agreed to stop his plan in exchange for the Doctor's TARDIS. The Doctor tricked the Master by saying that the Little England was his TARDIS. The Master attempted to cross the Doctor and leave him trapped in Hong Kong with the parasite. Instead, the Doctor took the parasite into his TARDIS while the Master went into the pub. The Brigadier came with the Doctor and they dematerialised to Mongolia. The Doctor dropped the parasite into a test area seconds before it was hit by a nuclear bomb and it was killed.

Instead of returning to Hong Kong, the Doctor and Alistair decided to travel through time and space. (AUDIO: Sympathy for the Devil)

He later travelled to Skaro where he helped Gillen and the other Thals to help stop the Daleks. He created at neutraliser which changed a Dalek to think that a Dalek was Davros. This created some dissidence among the Daleks. He suggested an alliance between the Daleks and Thals so that they could stop the Quatch. (AUDIO: Masters of War)

Other universes
In another universe, the Doctor didn't run away from the Master's attack of Hong Kong and he grew to like his exile. The Sixth Doctor and Evelyn Smythe accidentally travelled sideways in time and helped the Doctor stop "an annoying man" from infecting the United Nations with Krynoid pods. The exiled Doctor helped repair the Sixth Doctor's TARDIS by donating his TARDIS' dimensional control. (AUDIO: The 100 Days of the Doctor)

Appearance
This Doctor had grey, swept back, longish hair.

Initially he wore the attire of his previous incarnation. (AUDIO: Sympathy for the Devil)

By the time of his journey to Skaro he had taken to wearing a ruffled shirt, dark suit and cape. (AUDIO: Masters of War)

Behind the scenes
At one point, a myth arose in fandom that David Warner appeared in AUDIO: The 100 Days of the Doctor. In actuality, neither he nor "his Doctor" appear at all in the story, although the Sixth Doctor does refer to a character resembling this one.