The best advert for the phenomenon that is Deepak Chopra is Deepak Chopra. This 76-year-old Indian- American has come straight off a red-eye from Boston to the London hotel where we meet, pattering fast up the stairs for our interview in which he by turns quotes, word-perfect, many lines of Shakespeare and calmly savages some of his more vocal scientist critics.

This is Chopra’s distinctive mystic/ medical mash-up. He is both the multi-millionaire “guy from Oprah”, after his long association with the American chatshow superstar; and a physician. His latest and 93rd book, Living in the Light, is about the deeper philosophy behind yoga, and feels of a piece with someone who has appeared on Meghan Markle’s podcast. But his last book was on brain health, co-authored with a professor of neurology from Harvard.

While he was accused by some of the pseudo-science for a book entitled Quantum Healing, it is also true that research has recently come to support parts of his thinking about the mind-body connection in disease. The medical establishment and he once abandoned each other; now he is a part-time professor at the medical school at the University of California, San Diego. Deepak’s back, and in conversation, he doesn’t soften previous claims but doubles down.

“Every experience epigenetically modifies your body’s metabolism, second by second,” he says at one point in defence of his “quantum healing” theory. “And I don’t care what mainstream medicine thinks about that, they’re wrong.”

He is unembarrassed to bring religion into medicine, and to bring wealth into spirituality. He looks like a dinky Jeff Goldblum: he pairs his sober blue waistcoat (serious) with his trademark rhinestone-studded glasses (showbiz). As he talks he makes an angelic chiming sound: when asked the source he pulls up his sleeves. One wrist has a Buddhist bracelet chinking against a Sikh bangle. On the other is a smartwatch. We laugh — Chopra is an easy conversationalist — at how on-brand this is. “Spirituality and technology,” he says, “I’ve got everything covered.”

His flying visit to London is a favour to lend his starpower to the cause of Tibet: on Wednesday he introduced the premiere of the new documentary Never Forget Tibet: The Dalai Lama’s Untold Story. Chopra first met the Dalai Lama when he appeared at the Royal Albert Hall in London more than 30 years ago. Are they private friends? “He’s too much of a transpersonal identity to have a private relationship. But he makes you feel that way.”

Watching the documentary about the Dalai Lama’s dramatic escape from Chinese imprisonment in Tibet in 1959 now feels like a very relevant cautionary tale. “It could happen in Hong Kong, Taiwan, Korea, Ukraine. What’s happening in India and Pakistan isn’t comfortable either, if you look at the news right now.”

The film is important in another way: we have returned from the pandemic without learning the deeper lessons it could have taught us about caring for each other and the environment, he says. “As soon as we came back, it’s the same old thing. I don’t see any leader in the world except his holiness [the Dalai Lama], who’s making sense.”

He means they put their country’s interests first? “They’re putting the interests of themselves first. All of them.” Does Chopra have a soft spot for the British prime minister Rishi Sunak, given that he is a proud Hindu of Indian heritage? “It doesn’t matter that he is a ‘proud Hindu’,” says Chopra, gently mocking. “It’s what he does . . . I can’t say he has been doing all the right things.”

Does Chopra find the British a more sceptical lot? Some of his fiercest critics, Richard Dawkins, the evolutionary biologist, and Brian Cox, the physicist, are British. “No. I think the British contributed a lot to the world . . . but everything has a lifespan and I think Britain’s dominance is over. It lasted a few hundred years. And that’s pretty good for a small island.”

According to some ancient Indian teaching, he says, the first quarter of life is for education, the next “for family, fame, fortune all of that”, the third “you give back”. And the last? “You realise it’s all been a dream and you prepare for death. At that stage you don’t care what people think of you. I’m in my fourth stage.”

His career has spanned being championed by Oprah, to seeing Oprah interview one of his new supporters, the Duchess of Sussex. Did he help Meghan weather her recent storms? “Ultimately everybody has to take responsibility for their choices,” he says.

Did he ever use celebrity endorsement to advance his message? “Endorsements from celebrities don’t matter to me. In fact, sometimes they’re not that useful as people have their own opinion about who you associate with.”

Chopra doesn’t squirm when asked his worth. “I read on the internet that I’m worth something like $180 million but I don’t even look at my bank account. If I knew how much I’m worth, then that’s not good enough . . . to know your worth is to identify your self-worth, not your net worth.”

Does he feel that spirituality is incompatible with wealth, as in many religions? “Well, not in Indian philosophy,” he says, citing “artha” or material prosperity as one of the four aims in life. The proper use of money is “giving”, he adds. All of it came from his original epiphany, as an overworked, chronically run-down doctor. “My training is in neuroendocrinology. I was looking at the ‘molecules of emotion’ . . . serotonin, opiates, oxytocin, dopamine. There are many others. And they all happen to be immunomodulators. So if you have anger . . . or anxiety, all that leads to a depressed immune system. I’ve been talking about this for 40 years. When I started, I was vilified. Now what we were saying in the Seventies is part of medical school training. There are literally thousands of articles in peer-reviewed journals. I have a faculty position at the University of San Diego Medical School . . . And there’s a waiting list for people to take training in integrative medicine.” Does that feel satisfying? “To some extent, but I told you, I’m 76. It doesn’t matter.” Millions buy into his message but some scientists remain sceptical. One study used words randomly harvested from Chopra’s Twitter feed (which has three million followers), re-ordered by an algorithm to create a test for people’s tolerance for “pseudo-profound bullshit”. He says his critics “are behind the times, they’re my generation”.

“They say paradigm shifts happen one funeral at a time. So it’ll take a couple of generations.” How is his health? “I do two hours of yoga. I walk ten thousand steps. I sleep eight hours every night, other than when I’m jetlagged. I have no emotional issues. I would say I enjoy a joyful, energetic body. I experience compassion. I have a clear mind, and I’m light. I don’t have stress. In fact, I think stress is the worst use of imagination. Creativity is a good use of imagination.”

Does he get ill? “No.” Would he feel disappointed if he did? “No. I would question why, though. I see a lot of my colleagues in wheelchairs, having heart attacks, losing their memory. I feel I’m in my thirties, biologically. I like the idea of wisdom of experience and biology of youth.”

He tells me about a time on the wards when he gave a patient a cancer diagnosis, and their whole body slumped. “I’m sure if I’d measured his blood pressure, it would have been high. His platelets would have been sticky, and his body inflamed. Within 30 seconds, I realised I was looking at the wrong chart. So I said, ‘I’m sorry, that’s not you. That’s somebody else’. And he changed again in just one sentence.”

Does this also mean we are “to blame” for our own ill-health? “No. We should be educated about health and wellbeing so you can take responsibility. Responsibility means having the right response to a challenge. It doesn’t mean to feel guilty, which actually causes inflammation.”

Did his book Quantum Healing (1989) get him in a little trouble? “Not a little, a lot of trouble. I had to actually leave Boston [where he had been working at a hospital] because I thought my colleagues were going to fire me.” He says his friend, Rudolph Tanzi, Harvard professor of neurology, persuaded Chopra to reissue the book in 2015 with Tanzi writing a foreword. “That book has been a perennial bestseller. And I’m now doing a book with a physicist [Jack Tuszynski at the University of Alberta] called Quantum Body. Because I’m 100 per cent sure now that your body at a very fundamental level operates as a quantum mechanical object.”

Some physicists argue that Chopra misconstrues quantum theory. Dawkins has repeatedly tried to pin Chopra down, including during an interview in 2007, in which when pressed Chopra says his use of “quantum” is “just a metaphor”.

Chopra says to me: “The very critics that have been so hostile, including the luminary from England, Richard Dawkins. They’re inflamed. Look at their bodies. They have strokes.” I pause at this mention of Dawkins’s minor stroke in 2016, then reply: “Your revenge is living well.”

“No, it’s not revenge,” Chopra says. “It’s just validation. But even that’s not important.”

He seems to slip just out of grasp.

How would he define himself? “The moment you define yourself, you limit yourself,” he says, and quotes lines of poetry on the theme, drilled into him by the Irish Catholic monks at his primary school in Delhi. Shakespeare may have been the “greatest sage of all time” he says, quoting: “I hold the world but as the world ... A stage where every man must play a part, And mine a sad one.”

Never Forget Tibet: The Dalai Lama’s Untold Story will arrive in cinemas nationwide on April 19.