Doctor Who producers have revealed the new companion who will star alongside Peter Capaldi’s time lord in the hit science-fiction show’s 10th series.

British actress Pearl Mackie has joined the cast as Bill, who she told the BBC was “cool, strong, sharp, a little bit vulnerable with a bit of geekiness thrown in”.

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The new companion was introduced in a preview from a future episode where the Doctor and Bill are confronted with a killer Dalek — an alien war-machine which is Doctor Who’s oldest villain.

In the short scene the Doctor is clearly panicked, but Bill shows her wicked sense of humour during her first encounter with the mutant.

“Why do they keep saying exterminate?” she says.

“Wouldn’t it just be quicker to say kill?”

Mackie told the BBC she was incredibly excited to join the Doctor Who family.

“It’s such an extraordinary British institution, I couldn’t be prouder to call the Tardis my home,” she said.

Capaldi said Mackie is a “fine actress with a wonderful zest and charm, she’s a refreshing addition to the Tardis”.

Mackie replaces Jenna Coleman who played companion Clara for three series before she asked to be written out so she could take on a role in another production.

Capaldi was cast in 2013 as the 12th actor to play the Doctor.

The upcoming season will be the last for head writer and executive producer Steven Moffat, after which he will be replaced by Chris Chibnall.