Thomas Brewster

Thomas Brewster was an orphan and street urchin from Victorian London.

Meeting the Doctor
Thomas met the Doctor and Nyssa while he was being haunted by what he thought was his mother. After the Doctor helped him, he stowed away in the Doctor's TARDIS and accidentally set it on a solo flight. (BFA: The Haunting of Thomas Brewster)

Solo Travels
Brewster was able to gain limited control over the TARDIS. On one of his stops the TARDIS was taken from him for ransom and he was forced to work for the Doctor's old enemy, Gerry Lens. While working for Lens, Brewster meet the Doctor's old friends, the Brigadier and Polly. Together the three of them rescued the TARDIS from Lens and saved the Earth from dying and from a Coffinloader, a beast that feed on dying worlds. (CC: The Three Companions)

As the TARDIS began to self-destruct, Thomas was helped by an elderly Adric, who helped him return to London, a few months after his departure. The Doctor then invited him to join him on his travels, (BFA: The Boy that Time Forgot) but soon after he joined they returned to the location of one of his previous travels. (BFA: Time Reef)

Leaving the Doctor
Following their departure Brewster convinced the Doctor to take him to 2008 supposedly to see his future. But in actual fact he wished to re-meet a young woman named Connie he met whilst travelling in the Doctor's TARDIS alone. Thomas decided to stay in 2008 with Connie rather than travel with the Doctor and Nyssa. (BFA: A Perfect World)

Reunion With The Doctor
Brewster had been enjoying his life with Connie until tragedy struck. Connie was hit by a car and put into an irreversable coma. Alone and in a time he didn't fit, Brewster found the time machine he had built while under the control of the alien pretending to be his mother. He was trying to return to his own time when he was contacted by Symbios, a sentient planet. Symbios was being invaded by an alien robot species called the Terravore. Brewster provided Symbios with hosts who were riding the tube. After defeating the Terravores with the Doctor (now in his Sixth incarnation), Evelyn and DI Patricia Menzies, Brewster stole the TARDIS key, snuck aboard and held the Doctor and Evelyn at gunpoint demanding they take him back to his own time. (BFA: The Crimes of Thomas Brester)