Mackie, 28, replaces Jenna Coleman, whose character Clara Oswald left the show in 2015.

Filming for the next series of the long-running science fiction show will start this year but air in 2017.

Mackie, who graduated from Bristol Old Vic Theatre School in 2010, played Anne-Marie Frasier in Doctors in 2014 and is currently performing in the National Theatre’s West End production of The Curious Incident of the Dog in the Night Time.

“I’m incredibly excited to be joining the Doctor Who family,” she said. “It’s such an extraordinary British institution, I couldn’t be prouder to call the Tardis my home.”

‘Genuine delight’

She added: “Peter Capaldi is such a brilliant actor, and his Doctor is such a wacky and wonderful character, I can’t wait to see what adventures are in store for him and Bill throughout time and space.”

Mackie said her new character “Bill” was “wicked”, describing her as “cool, strong, sharp, a little bit vulnerable with a bit of geekiness thrown in”.

Capaldi said: “It is a genuine delight to welcome Pearl Mackie to Doctor Who. A fine, fine actress with a wonderful zest and charm, she’s a refreshing addition to the Tardis and will bring a universe of exciting new possibilities to The Doctor’s adventures.”

Doctor Who, which was first shown in 1963, is heading for its 10th season since it was reintroduced to schedules in 2005 after a gap of nine years.

Coleman joined the show in 2012, and starred alongside two Doctors, Matt Smith and Capaldi, the 12th Doctor who joined in 2014.

She asked to be written out and left to take on the role of Queen Victoria in a major ITV drama series.

In January, it was announced that the head writer and executive producer of Doctor Who, Steven Moffat, was stepping down from the show.

The next series will be his last, after which he will be replaced by Broadchurch writer Chris Chibnall.

Check out Pearl and Capaldi going against Daleks in the clip below: