A host of stars joined the King to see the first-ever film to premiere in a royal residence.
Finding Harmony: A King’s Vision, which will be released on Prime Video next month, was shown at Windsor Castle on Wednesday evening.
The film chronicles the monarch’s lifetime dedication to championing nature.
Among the 222 attendees were actors Benedict Cumberbatch, Sir Kenneth Branagh, Dame Judi Dench, and Stanley Tucci.
Musicians Sir Rod Stewart and Jools Holland also joined Oscar-winner Kate Winslet, who narrates the documentary.
Finding Harmony follows King Charles reflecting on the harmony between humanity, nature, and the environment, urging audiences to see themselves as part of nature.
Charles stated he “wasn’t going to be diverted” from his environmental campaigning, despite the criticism he faced over the decades.
Winslet described the documentary as a “special” and “important” work as she lifted the curtain on the event.
She gave some insight into Charles’s Harmony theory, telling guests before the viewing: “Harmony is a beautiful theory that invites us to see ourselves as a part of nature – not apart from it – and to tackle the world’s climate challenges using an interconnected, nature-first approach.
“You are about to see just how this theory has already been put into practice around the world, in so many inspirational ways, across a multitude of different cultures and sometimes for centuries.”
The film took six months to complete but has been “a lifetime in the making” for Charles.
She also spoke of his “passionate approach towards promoting the positive change ” he hopes to see across the globe.
Queen Camilla, the Duchess of Edinburgh and the Duke and Duchess of Gloucester were also in the audience.
In the 90-minute film made in collaboration with his charity The King’s Foundation for Amazon MGM Studios, the King says that the situation is “rapidly going backwards” with mankind “actually destroying our means to survival”.
But he expresses his hope “by the time I shuffle off this mortal coil” that there might be more awareness of the “need to bring things back together again”.
Charles is seen collecting eggs from his chickens at their “Cluckingham Palace” coop on his Highgrove estate, and reveals his love of a crispy baked potato, declaring that “red Duke of Yorks” are the best variety for this.
The documentary, which is being released on the streaming giant next month, describes how Charles, as Prince of Wales, emerged as a key figure on the environment over the years, making regular keynote speeches, despite “cries from some that he should take a back seat”, Winslet said.
Charles, in new footage, says: “I just felt this was the approach that I was going to stick to. A course I set and I wasn’t going to be diverted from.”
After an academic comments that the world is not on the “trajectory” needed to limit the worst effects of climate change, Charles remarks: “It’s rapidly going backwards, I’ve said that for the last 40 years, but anyway, there we are… I can only do what I can do, which is not very much – anyway.
“People don’t seem to understand it’s not just climate that’s the problem, it’s also biodiversity loss, so we’re actually destroying our means of survival, all the time.
“To put that back together again is possible, but we should have been doing it long ago. We’ve got to do it as fast as we can now.”
He adds: “Maybe, by the time I shuffle off this mortal coil, there might be a little more awareness… of the need to bring things back together again.”
Winslet, meanwhile, says: “While explaining his passion for organic gardening to the press, Prince Charles made a comment that has haunted him ever since.”
Archive footage of him describing how he talks to plants is included in the film.
Ian Skelly, co-author of the King’s 2010 Harmony book, said: “Those criticisms really upset him. He got treated very unfairly, seen very unfairly, and those of us that knew him better were quite upset by that.
“It was difficult to know how to respond, but I really felt for him.”
A spokesman for the King said the film was “not a conventional royal documentary”.
“There are no golden carriages here; no glittering crowns or crimson robes,” the spokesman added.
“Instead, this is a deeply personal exploration of ideas that have shaped His Majesty’s life and work: the interconnectedness of all things, the wisdom of traditional knowledge, and the belief that we can build a future that works in partnership with nature rather than against it.”
The spokesman added that it “sets a new high watermark for royal documentaries”.
The film is believed to be the King’s first documentary with a streaming platform.
The Duke of Sussex signed a deal with Amazon’s rival Netflix, which led to the series Harry & Meghan, in which the couple laid bare their struggles with royal life.
Amazon produced the series A Very Royal Scandal – a dramatised retelling of the King’s brother, Andrew Mountbatten-Windsor’s disastrous Newsnight interview.
Finding Harmony: A King’s Vision will be released on February 6 on Prime Video in more than 240 countries and territories worldwide.
