His portrait was taken by renowned photographer Rankin, and will be available on Monday.

In the magazine, the King talks about the importance of tackling food waste, adding he wants to use his birthday to shine a light on food insecurity and create a "lasting legacy to help others".

He will say: "Food need is as real and urgent a problem as food waste - and if a way could be found to bridge the gap between them, then it would address two problems in one.

"It is my great hope that this Coronation Food Project will find practical ways to do just that - rescuing more surplus food, and distributing it to those who need it most."

Speaking to Friday Night with Niall Paterson on Sky News, the editor of the Big Issue, Paul McNamee said: "Rankin's photographed a huge volume of people but hadn't photographed King Charles

"We knew that we had a relationship with the palace. Charles's support for the Big Issue... It goes back into the nineties.

"We talked to the palace. We realised there was something that could happen there. We managed to set up the portrait and the striking image. It's a...really great photograph.

"It's a great piece he's written as well."

Rankin said: "It was an absolute honour to shoot this specifically for the Big Issue and specifically around the Coronation Food Project, which I'm a big supporter of, and is something we don't talk about enough.

"I've always thought that he's a very resilient human being. I think that's what I got from him, that kind of steely determination."

Read more: Prince William spotted selling Big Issue in central London

Lord Bird, founder of the Big Issue, said: "It's grand that King Charles has his portrait on the cover of the Big Issue.

"His Majesty has long been a supporter of The Big Issue. He opened London Big Issue offices. During one opening, some 26 years ago, he met one of his old school friends who was then selling The Big Issue."

It comes a week after he opened the houses of Parliament, where a controversial measure to ban homeless people sleeping in tents was scrapped.

Elsewhere for the King's birthday celebrations, Highgrove Gardens in Gloucester will host afternoon tea for invited guests and "community champions" on Monday.

The King and Queen will then visit a food bank to launch The Coronation Food Project, and speak to staff and volunteers about combatting waste.