Can I ask you something?” says Greg Kinnear, slightly nervously, toward the end of our conversation. “Did you notice that I’m wearing a prosthetic nose?”

He is not talking about right now – he is on the other end of the line in a hotel room in British Columbia, so he could be sporting nothing but clogs for all I know – but rather how he appears in the new film Misbehaviour. In this British comedy-drama about the Women’s Liberation Movement protests that disrupted the 1970 Miss World event, he plays the US entertainer Bob Hope, who hosted the pageant that year and made no secret of his disdain for the idea of gender equality. A month earlier, the comic had appeared in a TV special, Bob Hope Looks at Women’s Lib, in which he imagined how different the TV networks would be if they were run by women: no televised sport but the offices would be spotless.

I tell Kinnear that I hadn’t noticed anything up with his schnoz; after a few minutes of the showbiz smugness, the slight squint and the right hand pressed flat against his body as though slipping inside an invisible pocket, it is possible to see him as Hope, despite the disparity in age (Kinnear is 56, while Hope was a creaky-looking 67 in footage from the event).

“Well, you sure know how to warm a guy’s heart,” he says. “But I’m worried about it. I said to my wife, ‘Is the nose too subtle?’ Because I think people are going to be asking: ‘What’s happened to Kinnear’s nose? Has he been drinking?’” It’s hardly Nicole Kidman in The Hours, I tell him. “Right. For her, it was like: ‘Oh my gosh, look at the nose!’ It was all anyone talked about. And here I am, my first interview out of the gate, and you’re saying: ‘I didn’t even know you were wearing one.’”

Kinnear may have been acting for a quarter of a century, but he still has the joshing, laid-back bonhomie that made him such an effective television presenter, just the right side of snarky and smarmy – first on Talk Soup, an irreverent Clive James-style roundup of eccentric cable-TV clips from the early 1990s, and then as a chatshow host on Later with Greg Kinnear.

“We went out in the wee small hours,” he recalls, “when you get your smokers and tokers.” It was from here that he was plucked by Sydney Pollack to star opposite Harrison Ford and Julia Ormond in a remake of Billy Wilder’s Sabrina, which led to his Oscar-nominated performance in As Good As It Gets as the gay artist forced to fall on the mercy of his misanthropic, bigoted neighbour, played by Jack Nicholson.

Playing Hope in Misbehaviour brought him back full circle to the sort of entertainer he used to be. Even before Kinnear’s TV career took off, he hosted a weekly hour-long show on Armed Forces Radio in his teens (as the son of a diplomat, he lived in Athens and Beirut before returning to the US to finish his education) on which he would, he tells me, “fill the hour with mindless talking and music.” While he has yet to acquire national-treasure status, there are certainly similarities between his career path and Hope’s. “It all began in radio for him, too, and that led to TV and a huge career at NBC – the same network where I worked – as well as movies. His job was so obviously a big part of who he was, part of his soul, even.” But as Kinnear is only too aware, Hope does not emerge from Misbehaviour with dignity. “We have a guy here living in a different era, which, when held up in today’s light and where we’re at, it does look, uh, slightly off.”

The film makes no secret of Hope’s infidelities; even before the feminist campaigners (Keira Knightley and Jessie Buckley among them) are pelting him with flour, his wife Dolores (Lesley Manville) is bracing herself for a repeat of the personal Miss World humiliation of a decade earlier, when he returned from his hosting gig with the winning contestant in tow. And that was only the mistress she knew about. His agent, Louis Shurr, once told a publicist: “Our mission in life is to keep all news about fucking and sucking away from Dolores.”

“I wasn’t so familiar with that side of him,” Kinnear says, “but I thought this was an interesting aspect of the movie. You’re taking this beauty contest, this event that was so commonplace and accepted, you know – ‘This is what we do, people.’ And to bring that up in 2020, it’s like I can’t think of anything that signals more clearly the cultural changes and shifts that have occurred, even just in the past few years. I tried to find the reality of who he was in that day and age and what he was there to do – to be that smiling, winking guy with these bathing-suit-clad beauties. And I think the movie shows that the times were changing around him, and he was caught off-guard by that.”

Does he think a persona such as Hope’s can be a straitjacket? “Well, you either change with the times or you don’t. And you can see he was very flat-footed in that moment and he doesn’t quite understand it. You see that situation all the time now and maybe in a more accelerated way in our current environment. It does show that progress is being made, whether or not we’re ready for it.”

Kinnear, who is in the middle of shooting a nine-part television adaptation of Stephen King’s The Stand, says that film sets are a very different place to be now. “The other day someone said: ‘Oh yeah, human resources are on set today.’ You know, a person who’s there to make sure people are feeling safe and following the rules and aren’t being compromised by someone who’s doing shit they shouldn’t be doing.’ And I thought: ‘Wow, where were human resources back in the 1990s?’”

Even setting aside the infidelities and his sexism, Hope is a prime candidate for “cancel culture”, which seeks to strike from the record the achievements of anyone whose moral and behavioural standards fall far below our 21st-century expectations. In the 1980s, for instance, Hope was using homophobic slurs and cracking Aids jokes. Kinnear asks me for a quick definition of cancel culture but it’s evident immediately that its principles are at odds with what he as an actor relishes in a role. “A person’s imperfections are always part of the great work of studying any character, showing all sides and finding the truth. Even the most noble, regal character still has flaws. For me, it’s a case-by-case basis. Egregious behaviour, where someone should have known better – well, I’m not sure you can write that off as: ‘Hey, the times were different!’ But I do think also there are many examples of behaviour where you can say: ‘Listen, this was a time when things were different and it’s unfair and ridiculous and pointless to some degree to pretend that their contribution was not meaningful.’”

There is a line that Kinnear delivers in As Good As It Gets that sums up the sentiment: “If you look at a person for long enough, you can see their humanity.” He practically trills when I mention it. “I love that line and I’m so glad you’re citing it. It’s true. There is always something to be discovered if you give it time.” To Kill a Mockingbird is much on his mind at the moment – he takes over from Ed Harris as Atticus Finch next month in Aaron Sorkin’s sellout Broadway adaptation – and he invokes that character here also. “Atticus says that you can’t really get to know a person until you get inside their skin and crawl around.”

As a father of three daughters aged between 10 and 16, he is keenly aware of the male bias in the movies that are greenlit. “It’s like turning an aircraft carrier around. It’s very slow. And you do feel that the inherent maleness of showbusiness for so many years is reflected in the vast majority of stories that get told. Misbehaviour I look at as a really entertaining story but it also has a strong female voice that I love and it isn’t told like a two-hour civics lesson. It’s just honest and powerful and it makes a dad of three daughters feel good.”

Will he show them the movie? “Oh my gosh, yes. The oldest one wants to take it to show at her school. In general, they are not particularly keen on watching anything that wasn’t made in the last four-to-seven minutes. For them, if a song didn’t drop in the last 15 hours, then it’s old.” I have to point out, though, that he said “drop” rather than “come out.” “How about that? They’re gonna be so proud of me. That’s the most contemporary term I’ve used in the past seven years.” The air of the bumbling dad is endearing. “I don’t do any social media and they are always telling me I don’t have much of an online footprint. They’re just used to me being a goofball.”

To the rest of the world, he’s Mr Nice. “I know the Nice Guy thing,” he sighs. “‘Good old Greggy Kinnear!’ As an actor, you can’t avoid who you are. You can’t get out of the way of your own persona. Jack Nicholson told me he thought 85% of who you are as an actor is just who you are, and the other 15% is what you can dial in and out. That sounds about right to me.”

His self-effacing nature, and those smiley, sad-eyed features, worked a treat in the likes of As Good As It Gets, Little Miss Sunshine and Ira Sachs’s heartbreaking Little Men. But his trustworthy image has also been used to subversive effect, such as in Paul Schrader’s disturbing Auto Focus, in which he played another beloved Bob – in that case, Bob Crane, the star of the US sitcom Hogan’s Heroes, who happened also to be a sex addict with a compulsion to film himself in the act. “Yes, well, that was a slight shift for me there,” he concedes. “I love that film. I was really surprised I got tapped to play the guy. But I didn’t think: ‘How are people gonna perceive me?’ It was just a damn good story. I try not to be too persona-oriented. Some actors are good at knowing where their sweet spot is and, for the rest of us, it’s a work in progress. I still have the excitement in my career of not knowing what the next page will be.”

• Misbehaviour is released in the UK on 13 March.