Doctor Who has introduced its first black portrayal of the titular Time Lord in its illustrious 57-year history.

Sunday's episode of the BBC sci-fi series saw the current incarnation of The Doctor, Jodie Whittaker, meet a previously-unknown past version of the character, in the form of actress Jo Martin.

This marked two major milestones for the series: the second time a female has played the time travelling extraterrestrial and the first time the character has been black.

'Definitively the Doctor': Doctor Who has been portrayed as a black Time Lord for the first time in the show's 57-year history

Some fans weren't sure whether or not Martin's appearance meant what it implied - but show boss Chris Chibnall has confirmed that this isn't 'a trick'.

He told The Mirror: 'The important thing to say is – she is definitively The Doctor. There's not a sort of parallel universe going on, there's no tricks. Jo Martin is The Doctor.'

Chibnall noted that the Top Boy star was credited in the same way John Hurt was credited when he appeared as another previously-unseen incarnation, who cropped up during the 50th anniversary special The Day Of The Doctor in 2013.

'That's why we gave her the credit at the end which all new Doctors have the first time you see them. John Hurt got that credit,' Chibnall explained.

Revelation: Sunday's latest episode of the BBC sci-fi series saw current incarnation of The Doctor, Jodie Whittaker, meet a previously-unknown past version of the character

Debut: Jo Martin's appearance marks two major milestones for the series - the second time a female has played the time travelling extraterrestrial and the first time the character has been black

Who is Jo Martin? Before her first appearance as The Doctor, Jo was most well-known for playing neurosurgeon Max McGerry in Holby City, who first appeared on the show in 2019. She also played Natalie Crouch in the BBC sitcom The Crouches from 2003 to 2005. In 2005 Jo also appeared in the blockbuster Batman Begins as a police prison official. Alongside other small guest roles, Jo also made an appearance in the second series of Fleabag, as Pam who worked at The Hot Priest's church. Advertisement

The character was introduced initially as a tour guide called Ruth Clayton, who pressed an In Case Of Emergency button as the Judoon invaded her hometown.

It's unclear where she fits in the mythology of previous Doctors - with many noting she did not recognise Whittaker's Thirteenth Doctor's Sonic Screwdriver, suggesting she came between Patrick Troughton's Second Doctor and Jon Pertwee's Third.

'There will be answers to some of these mysteries this series. But as ever with Doctor Who, answers often reveal new questions. It's all very deliberate,' Chibnall has assured.

He also revealed Martin wasn't aware she was auditioning to play The Doctor when she met the producers to read for them.

To be confirmed: It's unclear where Martin fits in the mythology of previous Doctors; Whittaker is the Thirteenth Doctor

Amazing: Jo also took to Twitter to share a glimpse of her Who-esque new look after the episode had aired

Movie star: Martin also appeared in 2005 blockbuster Batman Begins

Screen star: She also had brief roles in various TV series, and most recently has played neurosurgeon Max McGerry in Holby City

'We called her in and she read for it – with secret pages that didn't mention that it was the Doctor. But she's a massive fan of the show and I think she guessed.

'I had to ring her up and tell her and she was overwhelmed and thrilled. A lot of her family are fans and she kept that secret brilliantly for so long – nobody knew. We filmed it in the middle of last year.'

Martin is known for her role as Max McGerry in Holby City but has also appeared in the likes of Silent Witness, Casualty, Jonathan Creek, Fleabag, Still Open All Hours and Back to Life. She also appeared in 2005 blockbuster Batman Begins.

This is not the first time Doctor Who has featured a black Time Lord, as T'Nia Miller played Gallifreyan The General in 2015's Hell Bent, but this is the first time The Doctor herself has been played by a black actor.

Martin's casting comes after another Doctor Who star, Lenny Henry, claimed the BBC would rather cast a dog as the next Time Lord than use a black actor.

The 61-year-old told London's Colourful Radio that despite the introduction of Whittaker as the first female doctor, he thinks the channel still has a long way to go when it comes to promoting diversity.

Proven wrong: Martin's casting comes after another Doctor Who star, Lenny Henry, claimed the BBC would rather cast a dog as the next Time Lord than use a black actor

Teasing his appearance back in December, the Chef! star said: 'Why have we never had a black Doctor Who? They would rather have a dog do Doctor Who than a black person. There's no black people in Doctor Who'

Partnership: It's unknown what the future will hold for Martin's Doctor or for the rest of the series

Teasing his guest appearance ahead of the 12th season back in Decemeber, the Chef! star said: 'Why have we never had a black Doctor Who? They would rather have a dog do Doctor Who than a black person. There's no black people in Doctor Who.

'When Russell T Davis was doing Doctor Who there was so many black people in the show I rang up and said there are too many black people in the show — put in some white people, it's getting embarrassing.'

He added: 'We're still a long way away. The 'in' group who are in charge of everything are getting complacent.'

Aside from proving Henry wrong, the Doctor Who producers delighted fans with the arrival of Martin, sending them flocking to Twitter to exclaim their excitement.

Wild for it! Aside from proving Henry wrong, the Doctor Who producers delighted fans with the arrival of Martin, sending them flocking to Twitter to exclaim their excitement

'WE HAVE A BLACK DR WHO. THIS IS NOT A DRILL. WE HAVE A BLACK, FEMALE DR WHO!!!' one person exulted.

Another posted: 'Dear @bbcdoctorwho @DoctorWho_BBCA Thank you for finally giving a black nerd and other black nerdy adults and kids a Doctor who looks like us. You really dont know how monumental this was and how much it made me cry. Please don't let her be the only one ever.'

A third penned: 'Jo Martin as the Doctor!! Which incarnation exactly remains to be seen, and if she's even a canonical Doctor at all. All we know is she's the first black Doctor and in mere minutes she has owned the part!'

Doctor Who continues on Sundays at 7:10PM on BBC One.