The last time I saw Tony Curran, he was clad in armour, covered in mud and sitting in a trailer in the middle of Mugdock Country Park. 'Some of it is real, some of it is make-up,' he grinned, clearly unconcerned by all this grime. The Glasgow-born actor, who shot to fame in Andrea Arnold's 2006 debut Red Road, was between takes on Outlaw King, David Mackenzie's big-budget epic about Scotland's 14th Century warrior-king Robert The Bruce.

When we catch up, thankfully he's mud-free and basking in the Los Angeles sunshine and the satisfaction of an 'interesting year'. He's just finished shooting the new season of Ray Donovan with Liev Schreiber, playing a New York cop, and he's about to start the long-gestating movie of Deadwood, HBO's acclaimed western drama starring Ian McShane that was cancelled abruptly after three seasons in 2006. 'David Milch has written an incredible script,' he purrs. 'People are going to love that it's come back.'

For the most part, though, it's Outlaw King that's occupying our conversation. American actor Chris Pine plays Robert The Bruce, who famously defeated the English army of Edward I. Curran co-stars as Angus Og MacDonald, a loyal ally of Bruce. For research, Curran went to Iona, where MacDonald is buried. 'On Angus' sarcophagus it says: "One more push and Scotland is free, Lord of the Isles, my trust in thee." Those were words that Bruce had spoken about MacDonald.'

He delved into MacDonald's relationship with Bruce. 'One word I would use is loyalty. Angus believed in what Bruce was trying to do – albeit it was a very audacious, ambitious undertaking to take on the fighting force of Edward's army when they were outnumbered by so many.' He praises Mackenzie for crafting a film that isn't just blood and thunder but brings out Bruce's tenderness and compassion for his men. 'I think it's very important to have that.'

While Curran stops short of saying the film is waving the flag for Scottish independence, he prefers to see Bruce's fight with the invading Edward I in wider terms. 'There are oppressive regimes happening now all over the world. What's happening globally at the moment, there is a lack of tenderness, there is a lack of compassion that governments and certain individuals don't seem to have for their fellow man – which is a great shame.'

Curiously, Outlaw King – which was bankrolled by Netflix and will appear on small screens on Fri 9 Nov – is the second film the 48 year-old Curran has worked on this year to get its release via the streaming giant. The other was Matt Palmer's excellent thriller Calibre, which won the Michael Powell Award at the Edinburgh International Film Festival before bowing on Netflix last June.

It's since received five nominations at the upcoming Scottish BAFTAs – including Best Actor for Curran (his second nod in that category after Red Road). 'We're overjoyed at the response that it's had,' he says. 'Apparently a little known man called Stephen King tweeted about it!' Indeed, the horror maestro called it 'a genuine nail-biter'. Little wonder it's been a good year for Curran.

Outlaw King is available on Netflix and on a small cinema release from Fri 9 Nov.