Shah Rukh Khan says he knew Donald Trump would win. He watched the presidential debates while he was in Europe, but was at home in Mumbai to watch the election. He gave up when Florida swung red. “There’s always been a cycle for liberalism, intellectualism and populism,” he says. “I think the cycle has turned around the world. Here was somebody who was speaking the language the populists believe in, and maybe now is the time for that populist point of view.”

But isn’t what he generously calls populism an umbrella for racism, misogyny, Islamophobia, xenophobia and entrenched inequality, I ask. Khan won’t be drawn.

At 51, he is the biggest movie star in the world. According to Forbes, his earnings (an estimated $33m/£26.5m in 2016), 70-film back catalogue and international popular appeal put him well ahead of Hollywood’s mega-celebrities. Khan is insistent that he never wanted to be an actor. He had had one line in a play at college – “A letter for you, ma’am” – when his mum told their landlord that her son was an actor. The landlord’s father-in-law was a television director, and Khan ended up auditioning for a bit-part on the TV show Fauji (Soldier). He landed the lead role.

Shah Rukh Khan with Alia Bhatt in his new film, Dear Zindagi.

“And then I became famous,” he says, almost apologetically. “I didn’t really want to do it, but my mum died and I came to Bombay. I told my now-wife and my sister that I was depressed and wanted a change of scene, so I [left Delhi] for one year and it has now been more than 25 years. I still don’t know if I’m cut out for acting.”

He is joking, I think. We are surrounded by the trappings of Khan’s stardom: the central London hotel suite, the expensive suit and beautiful shoes, the bodyguards, and a small army of assistants – including one whose job it is to carry a hand-held mirror so Khan can check on his bouffy hair before photographs are taken. He chainsmokes throughout the interview, hotel regulations be damned. King Khan, as his fans call him, can get quite philosophical about his place in the world. Despite the edited retelling of his accidental career, I have never met someone so famous who is so frank about how hard they work to maintain that level of fame – and how much they need it.

“I make people happy. Whether I’m a good actor or not, whether I’m in a hit film or a flop, the one ability I haven’t lost is that I can go into the streets and out of 10, maybe six people will smile. That’s still a good average.” It’s true. He is understandably adored – even more so outside India – in a way unlike any of his peers; playing Khan to his public is perhaps his most successful role.

“I get very disappointed if I see people who aren’t enjoying what I’m doing and it’s not even value for money, it’s value for liking me. I need people to be happy after they’ve met me, if nothing else. You’re sitting with me now: you can see I’m a very boring person – but if you have an image of me being cool or funny or romantic from the films, I’ll do my best to live up to that expectation. If you tell me I’m not smiling enough, I will smile more.”

It’s an exhausting way to live. But Khan says he thrives on it, as the rest of the time can feel lonely on set or lonely at home. “I’m very shy and reclusive. I have to do the public things I do, and I do them with a lot of happiness. But I can’t take them home with me.” It’s the cliche of mega fame: the bigger your success, the smaller your world becomes. The more people love you, the fewer you truly trust and turn to. “I’m very sensitive, it’s why I’m very friendly and charming and everything people expect me to be, but I don’t have any friends.”

I’m not sure that’s wholly true.

“I get hurt very easily,” he insists. “I’m not very social. I don’t like keeping relationships.” For someone prone to periods of gloom, who admits that he can’t relax into a sunset, might it not help to have more than superficial friendships?

“There is hardly anyone I share my feelings with,” he says. “I believe your feelings are your own and no one understands them as well as you. Somebody can give it a good hearing, but nobody can solve the issue of your feelings, so I keep them to myself.”

He tells me the story of a friend who once wrote a biography and “completely destroyed” him. She said that Khan was over the hill, that his (now successful) production company would fail, that younger, better-looking actors would soon knock him off the top of the tree.

Khan in Dilwale Dulhania Le Jayenge, the 1995 comedy that transformed his career.

“When the interview was over,” says Khan, “we were going out with my son, and I joked to him: ‘Aryan, tell Aunty who is the biggest star’, and he said ‘Shah Rukh Khan.’ She wrote: ‘He will need more than his son to believe that.’ That was hurtful.” The memory clearly still pains him.

Khan came up playing villains in blockbuster hits – Darr (1993), Baazigar (1993) and Anjaam (1994) – before the 1995 comedy Dilwale Dulhania Le Jayenge transformed his career. It became the longest-running film in history – playing for 1,000 consecutive weeks in one Indian cinema – and established him as the country’s No 1 leading man, the “hero” in Bollywood terms, for an astonishing two decades. Emotive, screen-hogging performances thread together his biggest hits – Kuch Kuch Hota Hai (1998), Kabhi Khushi Kabhie Gham (2001), Devdas (2002), Veer-Zaara (2004) and My Name is Khan (2010) – but the standard-issue Khan energy is dialled down for his new film Dear Zindagi, in which he plays a subdued, rumpled sage with a thing for poetic aphorisms. No advance screenings are available, but the film’s tagline asks the audience to “find comfort in life’s imperfections”.

So, does he?

“I am not looking for comfort,” he says, grandly. “Because human nature, from the time of birth to wanting immortality, to finding happiness, these things are not going to happen in abundance or permanence. The quest of permanence in any of these things is futile and the sooner you realise it, the better.” Khan has a tendency to drift into circumspection, but as he admits, he spends a lot of time in his own head and reading – he mentions Paulo Coelho and Frank Herbert.

“Don’t suffer, live with it or learn to live with it. I’m at unrest. I’m at discomfort, not only with feelings, but a lot of things. I believe if you’re creative, then this will happen. So when people ask me: ‘Are you happy?’, I say: “No, I’m not so stupid to be happy all the time.”

Khan and Bhatt in Dear Zindagi.

From this, it seems fairly natural to segue into talk of the discomforting state of 2016, but Khan’s teams have told me there is to be no discussion of politics, religion, the depressing culture war between India and Pakistan, the rise of the far-right in India, or anything newsy that anyone might like to hear his opinion on.

Nonetheless, I venture to ask him whether, as an Indian Muslim living in an increasingly nationalist India, whose children are studying in the US and UK, he worries about his religion being demonised and scapegoated?

“No, we won’t go there!” It’s the only time his publicist, who, until then, has been idly scrolling through her phone, speaks up. Nevertheless, Khan ventures an answer.

“No, I don’t think so. I tell my kids, there are people who are completely mental who misuse and misunderstand the religion. Of course, you can always find an excuse that they were taught this wrongly when they were impressionable, but they are still wrong. No religion in any way condones violence, yet religious wars have been going on since time immemorial. There has to be a huge discussion in how we clear the name of any religion … but you can’t at this point.” Khan, who studied mass communication and journalism at university, speaks with a deep movie-trailer timbre.

He continues: “Look, there are people who believe our religion teaches violence, and it doesn’t. I know it, you know it. I have been brought up by Hindus all my life, I am Muslim by birth and I studied in an Irish Christian school. I know all religions to a certain extent and they are fundamentally the same – the majority of people understand that.”

Last year, Khan faced the most significant backlash of his career at home in India, with calls for him to be deported to Pakistan for having the temerity to call out the “extreme religious intolerance” that he saw growing in his country.

Matters have escalated dramatically in recent months; in September, a terrorist attack on soldiers in Uri, the India-occupied region of Kashmir, led to the Indian Motion Picture Producers’ Association banning all Pakistani actors, singers and crew from working in the industry “for ever”. The far-right party Maharashtra Navnirman Sena then called for all entertainment industry workers of Pakistani origin to leave India within 48 hours. Last month, Karan Johar, one of India’s best-known film-makers (and a close friend of Khan), released a video statement in support of the ban, begging audiences to watch his new film. Both his and Khan’s new movies feature Pakistani talent and face potential boycotts. It is a dangerous, hysterical precedent. How worried is Khan by it?

“I can’t get into that,” he says swiftly. “Look at my life now: I have 200 to 300 people who are attached to the business of Shah Rukh Khan. To affect the lives of some 250 people for a comment that I make, which is misread or misquoted or misunderstood by the people reading it? To me, to be able to carry on working as an actor and a star, it is a big responsibility to do it this way. I can’t let them down.”

So it is life-threatening?

“You have to understand, anything I say or discuss, there are people extremely happy to underline one thing and blow it out of proportion. It’s unfortunate for someone like me who did speak his mind. I only speak my mind to my kids now.”

Khan has three children (Aryan, 19, Suhana, 16 and three-year-old AbRam) with his wife Gauri, a film producer. The couple married in 1991, when Gauri was 21 and he was 25. “It is difficult to be married to a movie star,” admits Khan, when asked how they make an inter-faith (Gauri is Hindu), showbiz marriage work.

He continues: “We work because there is a lot of space. I like being on my own and that is provided without it being a thing. Nobody questions it, nobody talks about it: it takes a huge amount of sacrifice on the part of the spouse of a movie star. They need to have a certain level of confidence, belief, being OK with the hours of the star being away and still being able to maintain a certain amount of proximity for the family as a whole. But,” he emphasises, “space is the key thing.”

Does he worry about his children being spoilt by his wealth and fame?

“All the time. After their health, I worry that the shadow of my fame does not destroy their identity, that’s why I’ve sent them abroad to study, to figure out what they want to do. My kids are very balanced, mashallah, but to be children of a famous father … I want them out of this shadow. I wouldn’t even mind the shadow decreasing if it helps them.”

The ease with which Khan tracks and analyses his own fame might seem gauche, maybe even arrogant, but he is quite matter of fact about it. In 2010, on Jonathan Ross’s sofa, Khan was asked whether he ever goes out in disguise to avoid being mobbed. Incredulous, he half-joked that it was out of the question. “I worked very hard to be recognised. Why would I want to be in disguise?” He is also repeatedly generous in attributing his success to the women around him.

“I lost my father, then my mother, early on,” he says. “But the women in my life – the actresses – have helped me immensely. Everything I am is because of them. They are doing all that work and, mostly, I take away the credit for the film. I’m Shah Rukh Khan. None of them has become Shah Rukh Khan and I hope they do. I’m not trying to be pompous about myself. Madhuri Dixit has held my hand in those dancing scenes and I’m not leading her, she’s leading me. Juhi Chawla taught me how to do comic timing, Kajol taught me how to cry. They worked their asses off and then, at the end of the film, it’s ‘Shah Rukh Khan: the superstar’. And I know it. I can’t deny it. And I can never ever forget I am [there] because of women. All my chivalry, goodness, gentlemanliness only stems from the fact that it’s my way of saying thank you. They are fabulous in the films. In every film.”

It is disappointing then, I say, that he chooses to endorse Fair and Handsome – a controversial line of beauty products for skin bleaching – that piles pressure on “darker-skinned” Asians to feel ugly and ashamed. What follows is a three-part justification: Khan says it is legal, that he would never endorse women doing it, that he would never use the product himself. Hang on, what?

“I told them I’m not going to wash my face with it because I don’t do it, I don’t like it. They told me it’s a cream for men to clear up oil and dust, and at the end of the day you’ll get the beautiful girl. I can tell you now, no cream is ever going to get you beautiful girls unless you are beautiful with women. Guys, if you think you’re going to get women because of this cream, sorry. You’re not. I know they might not extend the ads now and I won’t do it, but I’m not selling fairness being better, I cannot sell beauty.”

But he literally is, I tell him, because that’s the product!

“But then you can ask about so many things I endorse. There are 27 of them and there will be a lot of contradictions. Suppose I’m selling luxury items, Louis Vuitton or Tag Heuer, would you ask me about selling products that are only unaffordable and against the poor? Now you and I are talking about it, if they don’t extend the campaigns, fine. But I am a walking, talking case in point: you don’t need to be good-looking. You don’t need to be fair, or tall, or have a special voice.”

• Dear Zindagi is now in cinemas worldwide.