The Winter King star Iain De Caestecker: 'Arthur is Uther’s illegitimate son and he has never felt Uther’s love'

Iain De Caestecker in a black leather tunic as Arthur in The Winter King
Arthur (Iain De Caestecker) faces huge challenges as he tries to unite Britain in The Winter King. (Image credit: ITV)

The Winter King brings the Dark Ages of 5th century Britain to life by offering a powerful new take on the Arthurian legends.

Based on Bernard Cornwell’s Warlord Chronicles trilogy of novels, the 10-part drama, which is dropping on ITVX on Thursday December 21 (available on MGM+ in the US), centres on young warrior Arthur (Iain De Caestecker), the illegitimate son of indomitable Uther (The Thief, His Wife and the Canoe star Eddie Marsan), the High King of Dumnonia, one of several warring regions of Britain. 

Cruel Uther banishes loyal Arthur, but as tensions mount in Britain and Arthur’s mentor Merlin (Nathaniel Martello-White), a powerful pagan politician, has concerns about the future, can Arthur return to save the country?

What to Watch caught up with Agents of S.H.I.E.L.D., Roadkill and The Control Room star Iain De Caestecker to find out more about The Winter King

The Winter King is full of action and adventure. How would you describe the show?

“It’s rooted in the reality of what it might have been like in that time period and it’s a grounded, human version of the legend. You've got the well-known characters, but with a different slant on them, so people like Merlin are more open to interpretation. And you have to see Excalibur [Arthur’s legendary sword]!”

Arthur (Iain De Caestecker) in a leather tunic alongside Merlin (Nathaniel Martello-White) in a white tunic in The Winter King.

Arthur (Iain De Caestecker) and Merlin (Nathaniel Martello-White) have a strong bond in The Winter King. (Image credit: ITV)

Tell us about Arthur…

“We go into his earlier backstory and his relationship with Uther, who is ruthless. Arthur is Uther’s illegitimate son and he has never felt Uther’s love. When Uther banishes Arthur from this kingdom that he has devoted his life to, Arthur goes away to Gaul and comes back as a forward-thinking leader.”

Eddie Marsan in a dark fur cloak as Uther in The Winter King.

Cold High King Uther (Eddie Marsan) banishes his illegitimate son Arthur in The Winter King. (Image credit: ITV)

What challenges does he face?

“He’s the person that Britain needs as danger’s brewing. It's a precarious position, paganism is competing with Christianity, there's an encroaching Saxon presence and in-fighting and the country is becoming fractured with power struggles.

“Arthur has to unite the different tribes but the stakes are high and you see the toll it takes to be a leader and the sacrifices and impossible choices you have to make. But he is also a man trying to reconcile the past and overcome childhood trauma."

Jordan Alexandra in a green dress as Guinevere stands opposite Iain De Caestecker as Arthur in a fur cloak as Arthur in The Winter King.

Guinevere (Jordan Alexandra) and Arthur (Iain De Caestecker) have a fateful meeting in The Winter King. (Image credit: ITV)

How do you see his relationship with spirited noblewoman Guinevere (Jordan Alexandra)?

“Guinevere has this effect on him that is unexpected, his world is tossed upside down and it's impossible to make the measured decisions he's accustomed to. We see a chink in his armour, which could be exploited in the future and he may be led by his heart rather than his head, and that’s dangerous…”

Derfel (Stuart Campbell) and Nimue (Ellie James) in brown tunics look into the distance in The Winter King.

Derfel (Stuart Campbell) and Nimue (Ellie James) become embroiled in Arthur's plans for Britain in The Winter King. (Image credit: ITV)

And what do you make of his bond with Merlin and his protegés — druidess Nimue (Ellie James), and Saxon Derfel (Stuart Campbell), whose life Arthur saves?

“Merlin is a surrogate father who took Arthur under his wing. Arthur has always been cynical about the gods, but he's respectful of Merlin and Nimue and their powers. And he has an unbreakable bond with Derfel and is protective of him. Derfel sees Arthur as somebody that can hopefully save the country like he saved him.” 

How have you found filming the brutal battle scenes?

“They are a challenge but it adds to the adventure. There's something different about the way Arthur and his men do things, they have more edge to them. They’re like the Navy SEALs or SAS of the Dark Ages. 

"I’d never been horse riding before but they are amazing creatures and big, gentle giants. It’s like driving a sports car that's alive!”

The Winter King is available on MGM+ in the US and all 10 episodes will air in the UK from Thursday December 21 on ITVX. It will be broadcast on ITV1 at a later date.

Caren Clark

Caren has been a journalist specializing in TV for almost two decades and is a Senior Features Writer for TV Times, TV & Satellite Week and What’s On TV magazines and she also writes for What to Watch.

Over the years, she has spent many a day in a muddy field or an on-set catering bus chatting to numerous stars on location including the likes of Olivia Colman, David Tennant, Suranne Jones, Jamie Dornan, Dame Judi Dench and Sir Derek Jacobi as well as Hollywood actors such as Glenn Close and Kiefer Sutherland.

Caren will happily sit down and watch any kind of telly (well, maybe not sci-fi!), but she particularly loves period dramas like Call the Midwife, Downton Abbey and The Crown and she’s also a big fan of juicy crime thrillers from Line of Duty to Poirot.

In her spare time, Caren enjoys going to the cinema and theatre or curling up with a good book.