As Doctor Who keeps bringing surprise twists and turns to the current series, and so it’s fair to say that there is a real buzz about series 12 so far.
And of course, part of that is down to the big names who've signed up to appear – so with that in mind here are the guest stars we can look forward to appearing throughout the run, as well as your guide to all the key players in the main cast and the actors who've appeared this year already.
Jodie Whittaker plays The Doctor
Probably the most iconic character in British sci-fi history, the Doctor is a Time Lord who has the ability to regenerate into a different person. The character is currently in their 13th incarnation – and first as a woman – and is known for their lovably eccentric nature.
Jodie Whittaker deftly dealt with the ugly and wholly undeserved backlash to her casting amongst a vocal minority of the fandom in her first run-out as The Doctor, battling with Witchfinders, giant spiders and the usual collection of frightening aliens and monsters. And it looks like even more terrifying prospects await her this season – including the return of the much feared Cybermen.
Prior to taking on the role as the Doctor, Whittaker enjoyed an extensive career on-screen including acclaimed roles in Broadchurch, the Black Mirror episode The Entire History of You and 2011 film Attack the Block.
Tosin Cole plays Ryan Sinclair
One of the 13th Doctor’s companions, Ryan was plunged into adventures in time and space last year - having previously been a warehouse worker in Sheffield.
Ryan often showcased great bravery at times in his first run of episodes, despite suffering from dyspraxia – which means he struggles with some tasks. Towards the start of series 11 he witnessed the death of his grandmother, Grace, and over the course of the series grew closer to her widower Graham.
Most of Cole’s on-screen roles prior to his casting in Doctor Who came in the world of soaps. He was a series regular in Hollyoaks and Hollyoaks later from 2011-2012, when he played Neil Cooper and earlier appeared in EastEnders: E20 as Sol Levi.
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Mandip Gill plays Yasmin Khan
Normally going by the nickname Yaz, Yasmin is a police officer from Sheffield – although she found little satisfaction in her work, which mainly revolved around relatively low-level and menial tasks. She was at school with Ryan, although at that time they were not on particularly close terms.
Being thrust into the action in series 11 clearly had a positive impact on Yaz, as she found adventuring in time and space a far more worthwhile vocation then policework, with one particularly poignant episode seeing her become part of her grandfather’s history during the Partition of India.
As with co-star Tosin Cole, before she stepped foot in the TARDIS Gill was best known for her stint in Hollyoaks, where she played Phoebe McQueen from 2012 to 2015. Other credits include a recurring role as Shazia Amin in Doctors and Nasreen Mahsud in an episode of Casualty.
Bradley Walsh plays Graham O'Brien
Graham is a retired bus driver and the step-grandfather of Ryan. Although Ryan had previously been suspicious of Graham, over the course of series 11 they became close, as they both dealt with not just monsters but also the grief of losing Grace.
Speaking to RadioTimes.com, Walsh suggested that Graham could face even more dangers in his second run of episodes. He said, “Graham’s journey, considering he is a bus driver from Sheffield, is the most extraordinary, life-changing things he has ever, ever, ever done. It’s just… it’s really difficult to put into words how someone from a normal environment would react to stuff like this.”
Walsh is a household name in the UK, but is arguably better known as a television presenter than as an actor, having hosted the immensely popular ITV game show The Chase since it started in 2009. In terms of his acting career, he is probably best known for a stint in Coronation Street, where he played Danny Baldwin between 2004 and 2006.
Sacha Dhawan plays O/The Master
Dhawan adds Doctor Who to an impressive small screen CV that already includes work on several of the nation’s most popular shows including Line of Duty, Mr Selfridge and Sherlock. He also has a past with Doctor Who - playing original director Waris Hussein in the 2013 television film An Adventure in Space and Time.
He was originally billed as playing O in the series, a former British intelligence officer who has been investigating alien life, but in a twist for the ages he was revealed to actually be the latest incarnation of that great foe of the Doctor - the Master.
Ian McElhinney plays Ko Sharmus
McElhinney was confirmed to guest star in episode nine, Ascension of the Cybermen, and played a character by the name of Ko Sharmus.
The veteran actor will probably be best known to audiences as Barristan Selmy in Game of Thrones and Granda Joe in Derry Girls, while other appearances include Taggart, Hornblower, Cold Feet, The Fall and The Tudors.
Julie Graham plays Ravio
Graham is returning to the Whoniverse having previously played villainous character Ruby White in the Sarah Jane Adventures back in 2010. This time round she'll be playing a character called Ravio, in episode nine.
She has appeared in a huge range of TV series since making her debut in Taggart in 1986, with prominent appearances in shows such as Survivors, Shetland and Benidorm.
Patrick O'Kane plays Ashad
Irish actor O'Kane, who is best known for his theatre work, is playing the "lone Cyberman" called Ashad. His previous TV and film work includes appearing in a 2014 BBC miniseries adaptation of Jamaica Inn, and a small role on series 2 of Game of Thrones.
Evan McCabe plays Brendan
McCabe plays a mysterious character called Brendan - who featured in an unusual subplot in episode 9, which took place in rural Ireland and saw the character join the Irish police force. Many have speculated as to the true identity of Brendan - with some even believing he could be another version of the Doctor.
This is McCabe's most high-profile screen role to date - he has previously appeared in episodes of TV series Striking Out and Berlin Station.
Seylan Baxter plays Tecteun
Previous roles for Baxter include appearances on Outlander and Lovesick, while she was recently seen in last year's BBC crime drama The Victim.
In the series finale of Doctor Who she will play a character called Tecteun.
Kirsty Besterman plays Solpado
Previous small screen appearances for Besterman include roles on Holby City, Silent Witness and Doctors.
She will be playing a character called Solpado in The Timeless Children.
Ritu Arya plays Gat
Gat is a Gallifreyan who works alongside Jo Martin's mysterious incarnation of the Doctor, and helped the Judoon track down the thirteenth.
Aryu is part of the regular cast for Netflix hit The Umbrella Academy, while other appearances include Humans, Sherlock and a long stint on Doctors - as well as film roles in Last Christmas and Daphne.
Steve Toussaint plays Feekat
Toussaint most famous international role is his appearance in 2010 blockbuster Prince of Persia, while he has turned up in a whole host of British TV staples, including Line of Duty, Silent Witness and Lewis, as well as several appearances in The Bill and Doctors. He will play a character called Feekat across the two-part series finale.
Alex Austin plays Yedlarmi
Austin appeared in three episodes of BBC miniseries The Interceptor in 2015 and has since had roles in Casualty and The Mallorca Files. He plays a character called Yedlarmi in Ascension of the Cyberman.
Matt Carver plays Ethan
Relative newcomer Matt Carver will star as Ethan in Ascension of the Cyberman - his first major TV role.
Rhiannon Clements plays Bescot
Clements will be making her small screen debut when she appears as Bescot in Ascension of the Cybermen, but won the prestigious Spotlight Prize in 2019 - which has previously been won by Judi Dench, Zoë Wanamaker and Jim Broadbent.
Lili Miller plays Mary Wollstonecraft Godwin/Shelley
The future author of Frankenstein and other works is brought to life by young actor Miller, who is a relative newcomer to TV having previous only filmed for Sky Atlantic's Gangs of London and a short film called Schlaf Night.
Jacob Collins-Levy is Lord Byron
The iconic poet and scandalous nobleman (known for Don Juan and Childe Harold's pilgrimage among other works) Lord Byron is played by Jacob Collins-Levy, who has previously starred in The White Princess (as crucial role Henry VII), Glitch, Bloom, Young Wallander, Pure, Barracuda and Gallipoli. He has also recently appeared in movie The True History of the Kelly Gang.
Maxim Baldry is Dr John Polidori
Polidori was a writer and physician associated closely with the Romantic movement headed by Byron, Shelley and the like, and is considered by some to have invented the "modern vampire story" with his short tale the Vampyre (which was written around the time of the episode).
He's played in Doctor Who by Maxim Baldry, most recently seen playing main character Viktor in dystopian drama Years and Years. Baldry's other work includes Hollyoaks, Strike Back, movie Last Christmas and the upcoming Lord of the Rings TV series, while as a child actor he appeared in HBO drama Rome and Mr Bean's Holiday.
Lewis Rainer is Percy Bysshe Shelley
A key Romantic poet, Shelley has been immortalised thanks to works like Ozymandias, To a Skylark, The Cloud and Masque of Anarchy. At the time the episode set he was estranged from his first wife Harriet and engaged in an extramarital relationship with future wife Mary.
In Doctor Who, Shelley is played by actor Lewis Rainer, whose screen credits include Grange Hill, Dani's House, Death Come to Pemberley, Endeavour, X Company, Casualty, A Hologram for the King and Wolfblood.
Nadia Parkes is Claire Clairmont
A former lover of Lord Byron, Clairmont was Mary Shelley's stepsister and later bore Byron's daughter Allegra.
In Doctor Who she's played by Nadia Parkes, who has previously appeared in The Spanish Princess as Rosa de Vargas.
Ian Gelder plays Zellin
Gelder has had an impressive career on stage and screen, with his most recognisable role being Kevan Lannister on Game of Thrones. He also has experience within the Whoniverse, having played Mr Dekker in Torchwood: Children of Earth.
In episode 7 of series 12, Gelder is playing a character called Zellin - who appears to be a rather malevolent-looking alien.
Aruhan Galieva plays Tahira
Galieva is a singer and actress, whose previous work includes roles in the Black Mirror episode Men Against Fire, and Joe Wright's 2012 film adaptation of Anna Karenina.
In episode 7, Can You Hear Me?, she is playing a character called Tahira, who is from Syria.
Buom Tihngang plays Tibo
Tihngang appeared in two episodes of last year's BBC One drama World on Fire, has done voice work for video games, has appeared on stage, and has a role in this year's series seven of Endeavour.
He plays Ryan's friend Tibo on episode 7 of series 12, in which he meets the Doctor and finds out where Ryan has been all this time.
Joana Borja plays Gabriela
Portuguese actress Borja was last seen in Martin Compston-starring drama Traces, and has also appeared in a number of projects in her native language.
Her character in episode six of Doctor Who is Gabriela, one half of a popular travel-vlogging duo, who we find adventuring in Peru.
Molly Harris plays Suki Cheng
Harris has previously appeared in an episode of Baptiste - and is also part of the cast for the upcoming film adaptation of Eoin Colfer's Artemis Fowl series of novels.
Suki Cheng, her character in Praxeus, is a scientist operating out of a lab in Madagascar.
Warren Brown plays Jake Willis
Brown currently stars in the action-packed Strike Back on Sky One while other appearances include Luther, for which he was nominated for a Critics' Choice Television Award for Best Supporting Actor in a Movie/Miniseries and ITV drama Liar, for which he was a member of the main cast.
In episode 6, he plays Jake Wills - a police officer taking a sabbatical who is brought to Hong Kong when he receives a desperate text from his astronaut husband.
Matthew McNulty plays Adam Lang
McNulty has recently been playing one of the main parts in Channel 4 drama Deadwater Fell - alongside former Doctor David Tennant - while his CV also includes recurring roles on ITV's Cleaning Up, BBC Two's Versailles, and Misfits.
In Praxeus, McNulty plays Adam Lang an astronaut who finds himself in trouble after he crash lands on the way back to Earth. He is the husband of Jake Wills - but the two characters have been experiencing a few relationship difficulties.
Thapelo Maropefela plays Arumu
This is Maropefela's biggest role to date - the South African-based actor has previously appeared in a short film titled Timêla.
In episode 6, Praxeus, Maropefela plays Arumu, a research assistant at Suki Cheng's lab.
John Barrowman plays Captain Jack Harkness
Barrowman had long been rumoured to be making a sensational return to the show, having last played the popular Captain Jack in 2011 - and so his appearance in the Fugitive of the Judoon, which had been kept extremely quiet, was a real event for fans of Who.
Barrowman's telly career has seen him appear in all sorts of roles - a judge on ITV's Dancing on Ice, a contestant on I'm a Celebrity and star of Dr Who spin-off Torchwood amongst the most high profile.
Judith Street plays Marcia
Experienced actress Judith Street's career has mainly been defined by her roles in the theatre, but she has made a few prior television appearances as well, including on Sky Original series Britannia and The Bill.
She will play a character called Marcia in episode 5, Fugitive of the Judoon, of which little is known so far.
Neil Stuke plays Lee Clayton
Best known for his roles on sitcom Game On and legal drama Silk, Stuke has also appeared in several staples of British TV drama, including Lewis, Agatha Christie's Marple, Silent Witness and Death in Paradise.
In Fugitive of the Judoon he will play a character called Lee Clayton.
Michael Begley plays All Ears Alan
This will actually be Begley's second appearance in Doctor Who - he played a character called Mulligan in 2011 episode The Curse of The Black Spot. This time around he plays a character with the rather amusing name All Ears Alan.
Other TV appearances from Begley include roles in EastEnders, Holby City and Foyle's War.
Goran Višnjić plays Nikola Tesla
Croatian-American actor Višnjić is probably best known to UK audiences for his role as Dr. Luka Kovač on the NBC television series ER, with other credits including a part in The Girl with the Dragon Tattoo and as a series regular on sci-fi show Timeless.
Višnjić will play Nikolas Tesla, the Serbian-American inventor best known best known for his contributions to the design of the modern alternating current (AC) electricity supply system. He is the latest in a line of actors who have played Tesla - with David Bowie and Nicholas Hoult amongst those to have portrayed him in the past.
On joining the cast he said, “I’ve always been a huge fan of Doctor Who, so when the offer to play one of my favourite people in history came, it made me so happy to be part of the show. And it turned into this awesome, dream job!”
Robert Glenister plays Thomas Edison
Spooks and Hustle star Glenister is no stranger to Doctor Who, having first appeared on the show way back in 1984, in Peter Davison’s final serial as the Doctor.
As with Višnjić, Glenister will be playing a real figure from history - the American Thomas Edison, who has been dubbed as the United States' greatest ever inventor and was recently portrayed by Benedict Cumberbatch in the film The Current War.
Speaking about his role he said, “I first appeared in Doctor Who in The Caves of Androzani at the tender age of 24 in 1984. “35 years later I got to be in it again at the not so tender age of nearly 60. How time flies!”
Anjli Mohindra plays Queen Skithra
Bodyguard star Mohindra joins the cast for episode four having previously played Rani Chandra on Doctor Who spin-off The Sarah Jane Adventures between 2008 and 2011. This time round, she'll be playing a different character - and one that the BBC hints will be "worlds away from her usual appearance."
As well as her work on Bodyguard and in the Sarah Jane Adventures, Mohindra's credits include roles in Mark Gatiss ghost story The Dead Room, The Missing and Midsummer Murders.
On joining the cast she said, “As a huge fan of the last series, it’s a bit of a dream come true getting to work opposite Jodie, Mandip, Tosin and of course after all these years, to work with Bradley again!"
"There’s something undeniably special about Jodie’s Doctor, and to be bringing some terror to the joint was rather fun indeed.”
James Buckley plays Nevi
Buckley was rumoured to be joining the cast as a guest star for weeks before his involvement was confirmed by the BBC, and he will appear as a character called Nevi in episode three, titled Orphan 55.
The actor is best known for his role as Jay Cartwright on popular sitcom The Inbetweeners and its two feature film spin-offs, while he has also appeared in a number of other shows including White Gold, Zapped and Red Dwarf.
On joining the cast, Buckley said, “It was surreal to be on such an iconic show and I’m really happy to be part of something so well loved. Hope everyone enjoys it!”
Laura Fraser plays Kane
Breaking Bad star Fraser will appear as Kane in episode three - with the Scottish actress promising that her character is "intense" and that it was a part she "couldn't resist".
She said, "I watched Doctor Who every week as a child, so it was a massive thrill to be asked to take part in such an iconic show."
Fraser's other roles include parts in The Missing and Traces.
Lewin Lloyd plays Silas
Young actor Lewin Lloyd will also be appearing in episode 3, playing a a character called Sylas - who seems to have a very similar hairstyle to James Buckley's character.
Despite only being at the early stages of his acting career, Lloyd has already racked up an impressive list of performances. Most recently he played Lyra's friend Roger Parslow in BBC One's acclaimed His Dark Materials adaptation, while other TV credits include Taboo and Netflix's The Alienist. In 2019 he also appeared in the films The Aeronauts and Judy.
Julia Elizabeth Fogle as Bella and Col Farrell as Benni
Fogle and Farrell are also set to guest star in Orphan 55, and appear to be playing an elderly couple - of which not much has been given away as yet.
Fogle - whois often credited under the name Julia Foster - is the mother of popular TV presenter Ben, and has been appearing on stage and screen since the 1960s, collecting credits on shows such as Casualty and films such as Dad's Army (2016).
Col Farrell - not to be confused with his somewhat more famous namesake - has appeared on many of the country's most beloved shows over a long and distinguished career, including Midsomer Murders, Heartbeat, The Bill, EastEnders, Casualty and I''m Alan Partridge.
Gia Ré plays Bella
Not much is known about the character Bella, who will be played in episode three by Gia Ré. This will be the most high profile role of Ré's career so far.
Stephen Fry plays C
Stephen Fry is British TV royalty, having appeared in a vast array of well-loved programmes as both an actor and presenter. He first shot to fame alongside Hugh Laurie in A Bit of Fry & Laurie, before featuring in legendary comedy Blackadder. He is also well-known for his role as the host of QI, which he fronted from 2003 to 2016.
Fry appeared in Spyfall the New Year episode of the show, playing C, a spymaster character who recruited the Doctor and her companions.
Speaking about his casting, Fry said, “Short of being picked for a British space exploration programme – and I readily concede that I’m past the age where I’d be considered (if I was ever the right age for such a posting) – then being in an episode of Doctor Who will certainly do as a very sweet second-place excitement.”
Lenny Henry plays Daniel Barton
Popular comedian Lenny Henry is no stranger to Doctor who showrunner Chris Chibnall or star Jodie Whittaker, having worked with the pair in the third series of Broadchurch in 2017. He is also well known for being a founder of Comic Relief and appearing in shows such as Tiswas, Chef! and The Magicians.
Henry also appeared in the New Year episode, as Daniel Barton a Bond-style villain and the CEO of a shady global tech company by the name of VOR.
Henry said of his casting, “It was absolutely brilliant to be welcomed into the fantastical world of Doctor Who. The nearest I have been to the TARDIS was when I played the Caribbean Doctor in the Lenny Henry Show, so as a life-long (hiding behind the sofa type) Doctor Who fan this is a very special moment for me.”
Sylvie Briggs plays Ada Lovelace
Doctor Who is no stranger to introducing real historical figures to the mix, and one of those to appear in series twelve is Ada Lovelace an English mathematician and writer from the first half of the nineteenth century who was known for her work with Charles Babbage.
She'll appear in Spyfall Part Two, portrayed by relative newcomer Sylvie Briggs, whose biggest credits to date include an appearance on comedy drama Cold Feet, and roles in a range of short films.
Aurora Marion plays Noor Inayat Khan
Ada Lovelace won't be the only historical figure appearing in Spyfall Part Two, with British World War II heroine Noor Inayat Khan also set to play a role in the episode. Khan was known for her service in the Special Operations Executive and was posthumously awarded a George Cross.
On Doctor Who, she will be played by Belgian, Greek and Rwandan actress Aurora Marion, who has appeared in theatre productions, short films and feature films across various countries.
Shobna Gulati plays Najia Khan
Gulati reprises her role from series eleven as Yaz's mum, Najia. Last series, she was particularly prominent in the episode Arachnids in the UK, in which the hotel where she had been hired to work as general manager was found to have a link to an outbreak of giant spiders. It remains to be seen how prominent a role Najia will have this time round.
Gulati has had a long and succesful career in the world of soaps, appearing in both EastEnders and corontaion Street, in addition to a role on Scottish soap River City. During series eleven, Gulati told RadioTimes.com, “Doctor Who for me personally was something that I’d always wanted to do as a child. I watched it, and the dream is that you will be the Doctor. Or, at the time when I was a child I wanted to be the Doctor’s assistant because they were always different and interesting."
Ravin J Ganatra plays Hakim Khan
Hakim is Yaz's father, and made a couple of appearances in series eleven and reprises his role for this series. Prior to joining the cast for Doctor Who, Ganatra had a prior connection to the series - having appeared in an episode of spin-off series Torchwood in 2006, as a character called Neil.
Bhavnisha Parmar plays Sonya Khan
Sonya was also introduced in series eleven, as Yaz's sister - and the two were shown to not get along particularly well, with lots of bickering between the pair. She was also seen to flirt a little with Ryan - perhaps there could be some potential romance in store in season twelve?
As well as appearing on Doctor Who, Parmar works as a voiceover artist, while her other on-screen roles include parts in comedies Brothers With No Game and Darren Has a Breakdown and the short film Aami and Frank.
Doctor Who continues on BBC One on Sundays