KING Charles rolled out the green carpet last night as the great and the good arrived at Windsor Castle to watch a new film on his environmental campaigning.

Charles, 77, hosted the first film premiere in a royal residence as stars including Kate Winslet and Dame Judi Dench arrived for the screening.

Also among the A-listers for the 90-minute documentary, which paints him as a baked potato-loving hippy, were Sir Rod Stewart and his wife Penny Lancaster as well as Benedict Cumberbatch and his other half Sophie Hunter.

Adding extra star quality were Sir Kenneth Branagh, Sarah Beeny, Stanley Tucci and gardening royalty Alan Titchmarsh.

Before the screening in Windsor’s Waterloo Chamber, the audience stood for the King and Queen Camilla, who, in keeping with the theme, wore a green dress by Anna Valentine plus a brooch from the King’s Foundation.

Winslet, the film’s narrator, said: “Your Majesty, it is thanks to your great vision and foresight in protecting our natural world we’re all here this evening.

“Filming may have taken place across a short six months, but Your Majesty I know that for you, this documentary has been a lifetime in the making.”

The documentary, Finding Harmony: A King’s Vision, explores the origins, evolution and scientific foundations of Charles’ harmony philosophy as set out in a 2010 book.

It follows him through the speeches he gave in his 20s on green issues and shows off his achievements at the royal estates of Highgrove and Sandringham and at Dumfries House, Scotland.

Despite illustrating how he was years ahead of public opinion on the merits of growing and eating organic produce, the Amazon Prime Video film recalls how he was teased over his views.

Winslet says: “While explaining his passion for organic gardening to the Press, Prince Charles made a comment that has haunted him ever since.”

It is a reference to a 1986 interview in which he said: “I just come and talk to the plants, really — very important to talk to them, they respond.”

Ian Skelly, co-author of the King’s book, Harmony: A New Way Of Looking At Our World, said: “Those criticisms really upset him. He got treated very unfairly, seen very unfairly.

“Those of us that knew him better were quite upset by that. It was difficult to know how to respond. I really felt for him.”

While discussing organic growing, His Majesty is seen in the film admiring spuds growing in his gardens at Highgrove, Gloucs.

He says: “If you want a decent baked potato, which I love, you’ve got to have the crispy skins.”

He is also filmed carrying a basket to collect eggs from a coop which has on its door a sign reading Cluckingham Palace.

The film also features footage of Princes William and Harry with their father.

And in it, dairy farmer Patrick Holden, CEO of the Sustainable Food Trust, tells the documentary: “Jamie Oliver said he (Charles) was a bit of a hippy and I think that’s probably true.”

Charles is also seen watching archive footage of his campaigning speeches.

Describing his harmony philosophy, he says: “It all boils down to the fact that we are actually nature ourselves. We are a part of it, not apart from it, which is really how things are being presented for so long.

“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.”