Robert Duvall on The Judge, Brando, and Ally McCoist: Why his policy is to follow the writing

Robert Duvall gives a typically grandstanding performance opposite Robert Downey Jnr in The Judge – one for which he has just received his seventh Oscar nomination. Duvall, whose film credits range from To Kill a Mocking Bird and The Godfather to Apocalypse Now and Tender Mercies, plays a small-town judge. The judge's absolute certainty in his own righteousness is undermined when his memory begins to fail. He is involved in a hit-and-run case – and it seems he may have taken the law into his own hands.

"It was hard work," the 84-year-old Duvall says of the role, for which he also received a Golden Globe nomination. "You get 23 days on an independent movie. You get 60 days on a big movie but the 60 days seems like 23 because you are working intensely each day."

In one scene, we see the judge in a state of panicked incontinence – a once mighty figure who can no longer even look after himself. Ask Duvall how he prepared for such a harrowing scene and he simply says that he "followed" the writing.

Following the writing has been Duvall's policy right since the start of his career. In the late 1950s, playwright Arthur Miller came to see him play Italian-American longshoreman Eddie Carbone in an off-Broadway production of Miller's A View from the Bridge.

"He [Miller] visited the rehearsal once or twice. Some friends of mine from East Harlem, where they have organised crime, they said Arthur Miller reminded them of a 'made man.' When you become successful in a (crime) syndicate, you're a 'made man'. He had that New York accent and he was dressed so neatly. He reminded my friends from that area of a 'made man' although he was a very educated guy and very intellectual."

It's an intriguing observation and can't help but make you think that his memories of Miller fed into the well-dressed but understated lawyer Tom Hagen, Don Corloene's adopted son, Duvall played so memorably in The Godfather (picking up his first Oscar nomination in the process way back in 1973.)

Duvall's big movie break came when writer Horton Foote (later to script Duvall's Oscar-winning film Tender Mercies) recommended him for the role of the reclusive Boo Radley in To Kill a Mockingbird (1962). Duvall points to Foote and to Francis Ford Coppola (who cast him in The Rain People, The Godfather and Apocalypse Now) as being "somewhat instrumental in helping me in my beginning years as an actor". It is a source of annoyance to him that Foote, in spite of two Oscars and huge output of plays, isn't better known.

Having started as a Method-style stage actor, Duvall has now all but given up theatre. "I haven't done theatre in many, many years. The great Eleonora Duse, when she came to the United States, said she refused to do (a performance) eight times a week. I think eight times a week is a bit of a burden. If I had to go back to the theatre right now, I could do it but I prefer film because you get to travel and to meet people."

Duvall is hoping to be back in the saddle again soon. He is planning a new film, The Day the Cowboys Quit, adapted from a book by Elmer Kelton. "It's about some cowboys who went on strike against some big ranch owners who would not let them have their own band of horses and small herd of cattle."

James Caan (a friend from Godfather days) has agreed to appear in it and Peter Berg is in talks to direct. The hitch now is finding the financing. Westerns aren't exactly a popular genre even if Duvall sees them as the quintessential American form of storytelling. "You (in Britain) have Shakespeare, the French have Molière, the Russians have Chekhov and we (in the US) have certain things and the Western is one of them!" he declares.

If the film does go ahead, the octogenarian star will be on horseback himself. He confides that when he was appearing opposite John Wayne in True Grit (1969), the Duke used to cheat a little bit when it came to the close-ups of the horseback scenes.

"They put a two-by-four (piece of lumber) on the back of a pick up truck and the saddle on the two-by-four and he sat on that for the close-ups."

There won't be any such short cuts from Duvall. To his great pride, he was made an honorary Texas Ranger in 2011. "They're like the State version of the FBI but to me more effective." The veteran star describes TV mini-series Lonesome Dove, in which he played a former Texas Ranger, as "probably his favourite part ever". He is also very proud of another new film, Wild Horses, which he directed and in which he stars opposite James Franco and Josh Hartnett.

One of the most incongruous credits in Duvall's very lengthy filmography is Scottish football drama A Shot at Glory, in which he co-starred with the Scotland international Ally McCoist. The film was shot in the East Neuk of Fife, not a location often visited by Hollywood stars.

What brought Duvall to Scotland to play dour Scottish football coach Gordon McCloud in a lowish-budget sports movie?

"The director came up with a writer. You know, we went up there and jumped in there and did it. It happened to be about Scottish football. I do like soccer, football, a lot. The Scottish are good at it but not great," Duvall states. "Somebody said that when they (the Scots) play Brazil, there is one team that thinks they're the greatest and the other team that knows they're the greatest."

Duvall admiringly describes McCoist as being "sharp as a tack". No, he hasn't seen the former Rangers striker for a number of years. "I think he was the manager of Rangers until recently. I don't know how successful he was. But it's a very difficult to be a manager or coach because as soon as you're hired in any given sport, if you don't do well right away, they're looking for an excuse to fire you or get rid of you."

The football coach was one of a very long line of authority figures that Duvall has portrayed on screen. Some of his best roles have been as military men, for example as Lieutenant Colonel Kilgore yelling about the smell of napalm in the morning in Apocalypse Now or as the martinet Marine officer with a disastrous family life in The Great Santini.

Duvall is the son of a US Navy admiral and acknowledges that his own military background was useful for such roles. However, he also points out his father was a relatively quiet man.

"I was in the army myself and I was drawn to observing people in the military," Duvall says. "I had a respect for the military although I didn't want to be in it. I wanted to do it as accurately and correctly as possible without demeaning or patronising any given part I did when I was playing a military man."

Look over the many films in which Duvall has appeared over the past 50 years and you can't help but notice the number of screen greats with whom he has worked: Wayne, Gregory Peck, Marlon Brando, Frank Sinatra, Steve McQueen, Clint Eastwood, Laurence Olivier and Peter Finch. He singles out Brando as the one who influenced him most: "He was kind of like the godfather of young actors."

Even now, in his eighties, he isn't embarrassed to acknowledge his childlike admiration for such peers. "It's always good to have heroes. If you don't have heroes, at one point in your life, you don't grow. Nobody has all the answers… it is healthy and legitimate to have heroes."