Colin Baker was born in 1943 in the Royal Waterloo Lying-In Hospital in London during an air raid. He spent his earliest years in London with his mother, while his father served in the armed forces. He narrowly avoided an early death during the wartime blitz when a piece of flying shrapnel just missed him, embedding itself in the side of his cot. After the war, Baker's father took a job as managing director of an asbestos company in Manchester. The family moved north to live in Rochdale, although Baker attended school in Manchester.

It was during his early schooling that - through the mother of one of his fellow pupils, who was a casting director at Granada TV - he had his first experience of acting. It was 1954 and the series was called My Wife's Sister (1956), starring Eleanor Summerfield, Martin Wyldeck and Helen Christie. Colin Baker went on to attend St. Bede's College in Manchester, where he was invited to take part in their annual productions of Gilbert and Sullivan operettas. The twelve-years-old Baker appeared in the chorus for a production of "Yeoman of the Guard" and, a year later, landed a more major part - playing the female lead, "Phyllis" - in "Iolanthe".

After completing his schooling, Baker went on to study law. One day during this period, he and his mother went to see an amateur production of "The King and I" at the Palace Theatre, Manchester. Inspired by the performance and encouraged by the president of the company that had staged the Amateur Dramatic Society and quickly became hooked on acting. Baker took a job as a solicitor but, as time went on, became less and less interested in this career. Finally, at the age of twenty-three, he decided to become a full-time actor.

Baker joined the London Academy of Music and Dramatic Art (LAMDA), where he trained for three years. At the end of this, he was summoned with two of his fellow students to see the head of the drama school, who gave them rather gloomy predictions for their future prospects as actors and suggested that they seek alternative careers. These predictions proved somewhat wide of the mark as not only did Baker go on to great success but so too did his fellow students - David Suchet (who amongst many other achievements starred in LWT's award-winning productions of Agatha Christie's "Poirot") and Mel Martin (whose numerous credits include the series Love for Lydia (1977), also for LWT). After leaving LAMDA, Baker took a temporary job driving a taxi in Minehead in order to be near his then-girlfriend. He then received a call to come to London to audition for a part in a BBC2 drama series called Roads to Freedom (1970), which he won. This led to further TV roles, including two more for BBC2: "Count Wenceslas Steinbock" in "Balzac's Cousin Bette" (1971) and "Prince Anatol Kuragin" in an ambitious twenty-part serialisation of Leo Tolstoy's "War and Peace" (1972-72). He also took on a wide range to theatre work, including several William Shakespeare festivals, appearing in productions of "Macbeth" and "Hamlet".

In the mid-seventies, Baker landed the role that would make him "the man viewers love to hate". This was "Paul Merroney" in the BBC1 series The Brothers (1972). After "The Brothers", Baker married actress Liza Goddard, who had played his on-screen wife in the series, but the marriage eventually ended in divorce. Baker later married actress Marion Wyatt. Theatre work kept Baker almost constantly busy for the next five years including appearances in everything from comedies to thrillers, as well as more Shakespeare. He also had a few further TV roles, including one as "Bayban" in "Blake's 7: City at the Edge of the World" (BBC, 1980) and one opposite Nyree Dawn Porter and Ian Hendry in the drama series, For Maddie with Love (1980) (ATV, 1980).

Baker's next TV role after "For Maddie with Love" was as "Maxil" in the Doctor Who (1963) story, "Arc of Infinity". Shortly before Baker took the role of the Doctor on "Doctor Who", he and his wife suffered the loss of their baby son, Jack, to cot death syndrome. Baker subsequently became a passionate fund raiser for the Foundation for the Study of Infant Deaths, with many of is personal appearance fees being donated to the charity. Baker's time as the sixth Doctor was cut unexpectedly short, initially by BBC One controller Michael Grade's hiatus between the twenty-second and twenty-third seasons and then by the decision of Grade to oust him from the role.

After his departure from "Doctor Who", the actor returned to the theatre, appearing in highly successful runs of "Corpse" and "Deathtrap" and having a four-month stint in the West End farce, "Run for Your Wife", with Terry Scott. TV work included a guest appearance in the BBC's Casualty (1986) and presenting assignments on programmes for the Children's Channel. After directing a play called "Bazaar and Rummage", Baker was asked to play the Doctor once again - this time on stage, taking over from Jon Pertwee in the Mark Furness Ltd production, "The Ultimate Adventure". This tour proved to him that, despite the brevity of his time as the Doctor on TV, he had amassed a loyal following amongst younger viewers.

In the 1990s, Baker had continued to pursue a successful career, mainly in the theatre. He has made regular appearances in pantomime, and his stage work has included roles in the musical adaptation of Charles Dickens' "Great Expectations" and in a comedy entitled "Fear of Flying". He has also starred in the "Stranger" series of videos made by Bill Baggs Video, alongside a number of other actors known for their work on "Doctor Who".