Thomas Brewster

Thomas Brewster (born 1846 or 1847) was an orphan and street urchin in Victorian London.

Meeting the Doctor
Thomas met the Fifth Doctor and Nyssa on 14 November 1867 while he was being haunted by what he thought was the ghost of his mother, who had died in 1851. 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 gained 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 met the Doctor's old friends, the Brigadier and Polly. The three of them rescued the TARDIS from Lens and saved the Earth from dying and from a Coffinloader, a beast that fed on dying worlds. (CC: The Three Companions)

As the TARDIS began to self-destruct, Thomas was helped by an elderly Adric, who got him back to London a few months after his departure. The Doctor 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
After they left, Brewster convinced the Doctor to take him to 2008 supposedly to see his future. In fact, he wished to be reunited with a young woman named Connie whom he had met whilst travelling in the Doctor's TARDIS alone. Thomas decided to stay in 2008 with Connie rather than continue travelling with the Doctor and Nyssa. (BFA: A Perfect World)

Reunion with the Doctor
Brewster enjoyed his life with Connie until tragedy struck. Connie was hit by a car and fell into an irreversable coma. Alone and in a time where he didn't fit, Brewster found the time machine he had built while under the control of the alien pretending to be his mother in 1867. 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 Smythe 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 Brewster)

Behind the scenes

 * Along with Charley Pollard, Brewster is one of only two companions created by Big Finish to travel with two incarnations of the Doctor, namely the Fifth Doctor and the Sixth Doctor. The only other Big Finish created companion to have met two Doctors is Evelyn Smythe, who served as a companion of the Sixth Doctor for several years and met the Seventh Doctor in BFA: Thicker than Water and BFA: A Death in the Family.