The cold, dead eyes that once stared at Walter White with contempt are moist and red. “I’m not feeling well today,” groans Jonathan Banks, as he fumbles with a tin of cough lozenges. “And my back is killing me.” This is a somewhat disconcerting introduction to one of the great on-screen heavies. Banks, now 69, has been an intimidating presence in movies and TV for over four decades, only ascending from the ranks of naggingly familiar character actors in the last few years with his portrayal of bone-weary crime-scene fixer Mike Ehrmantraut in Breaking Bad and its prequel, Better Call Saul.

Banks received best supporting actor Emmy nominations for playing Ehrmantraut in both. Back in 1989, he was nominated for another deadpan supporting role, that of cynical detective Frank McPike in Wiseguy, a show about undercover cops. That series, I tell Banks, with its dense serialised story arcs, its antihero lead and its blurring of good and evil, was fairly prescient about the direction US TV has taken. Banks’s gloom lifts, both at the mention of Wiseguy (“It spoke to the darkness in all of us”) and the state of the small screen. “If you had ever told me that the finest film work was going to be done on television, I wouldn’t have believed it. You could take a film like Spotlight or The Big Short and either of them could easily have been done on TV; that’s the quality of writing. It’s not that I don’t enjoy a good mystery that comes and goes in a hour. I do but, God, Breaking Bad and Saul unfold like novels.”

Banks spent much of the 1980s playing bad guys on high-rated series such as TJ Hooker and Simon & Simon. This was an era when the term “the best TV show ever made” was rarely bandied about. We now live in a different time. The Sopranos was hailed as the best TV show ever made somewhere in the middle of its first season. So was Mad Men. The Wire was anointed in its third year. So how does Banks feel about Breaking Bad’s place in the pantheon of best TV shows ever made?

“I don’t think it’s up to me to say, because I’m a part of it, but if it is the best show, it’s because it was consistently good,” he says. “There’s some shows you’ve mentioned where I see a weakness here, a weakness there. I love Boardwalk Empire but there were moments where I thought it didn’t have the constant through-line that Breaking Bad did and Better Call Saul does.”

Banks made his Breaking Bad debut at the end of the second season in 2009. In 2012 – late watchers’ spoiler alert! – he took a bullet to the stomach at the hands of Walter White. Other cast members have described how series creator Vince Gilligan broke the news of their characters’ imminent deaths to them by gently inviting them into his office for a chat. Banks grins at the memory of Mike’s notice of termination.

Jonathan Banks and Bob Odenkirk in Better Call Saul Season 2. Photograph: Ben Leuner

“I always knew Mike was going to get knocked off,” he says. “We were at Aaron Paul’s pre-wedding fiancee party, whatever the word is…” He looks confused for a second and then brightens. “Engagement! That’s the word I was looking for. The hors d’oeuvres were coming around. Vince was standing there with me and Aaron’s father-in-law-to-be, and Vince was going on about how good the hors d’oeuvres were and I went: ‘Hey motherfucker, what about my future? How am I going to die?’ That’s when he told me.”

Mike Ehrmantraut may have expired in 2012, but the character is still alive and eternally pissed off in Better Call Saul. The notion of a Breaking Bad prequel focusing on Bob Odenkirk’s shyster lawyer, Saul Goodman, nonplussed many fans. Until they saw that Vince Gilligan and co-creator Peter Gould were making their own Death Of A Salesman, a weekly catalogue of the small indignities and humiliations assailing hard-working Jimmy McGill before he reinvented himself as Saul Goodman. Mike Ehrmantraut makes fleeting appearances in the first few weeks, but the mid-point of the series is all his. In the episode titled 5-0, the character’s back pages are finally revealed. He was a corrupt Philadelphia cop with a son who joined the same police department. Fearing that his boy’s strong moral code would make him a target for the station’s dirty cops, Mike persuaded his son to take a few bribes. The dirty cops killed him anyway. After gunning down the policemen responsible, Mike confesses to his daughter-in-law Stacey (played by Irish actor Kerry Condon): “I made him lesser. I made him like me. I broke my boy.”

Banks exhales when reminded of the scene:“[Writer] Gordon Smith wrote me a love letter and when somebody takes that kind of work and he gives you it, I was going to make goddamn sure I would work to the very best of my ability and I would be lying to you if I didn’t tell you I loved the pay-off. The dad kills the motherfuckers that killed his son.” He leans forward and pins me with those unforgiving eyes: “Listen, if I’d be king, would I outlaw the death penalty? Probably. If I’d be me, I’d kill the motherfuckers. Let me ask you: how many fathers in the world, if somebody murdered their son, wouldn’t enjoy killing them?”

Jonathan Banks as Mike Ehrmantrautin in Breaking Bad. Photograph: Ursula Coyote

5-0 won Banks his third Emmy nomination. Discussing that climactic scene with Condon still makes him emotional. “I’ve had friends that have lost children and I look at them and I don’t know how they survived,” he says. “In both cases, I’m thinking the only reason they didn’t blow their brains out was that they had other children to raise. But I don’t think that has anything to do with Mike. Mike will never, ever, ever forgive himself.” Experiencing Mike’s guilt over his son gives audiences a better understanding of his affection for Jesse Pinkman, Walter White’s hapless sidekick in the crystal meth business in Breaking Bad. “I don’t know if Mike thought he could ever save Jesse, he could only tell him to go away from the business. I don’t think he ever wanted to take Jesse on as a son, but I think he instinctually loved him. Mike has a lot of love in him. He can’t put it in words. He knows he’s broken and it’s very easy for him to see how broken other people are.”

The day before I met Banks, Abe Vigoda, the character actor best known for playing Sal Tessio in The Godfather, died. Aged 94, he was working up until the end. Thinking back now, it may have been a little morbid to ask a sick, sweating, coughing actor with a bad back whether he sees himself going out like Vigoda, or emulating Sean Connery, Joe Pesci and Gene Hackman by walking away without a word. “I think I’d rather go the way they did,” he answers, gamely. “The first actor I was aware of was William Powell, who did The Thin Man, and when he was 60, younger than I am, he walked away. There just comes a point. I’m close to that point. I love being at home. My wife and I for the first time are alone. My boys have both left. I like my wife. I’m stupid in love with my wife and always have been. I’m going to be maudlin, but I have a great life.” With that, Banks closes those terrifying eyes and lets the cough medication whisk him away to a happier place.

Better Call Saul returns to Netflix on 16 February, with new episodes weekly.