The Prince of Wales says he will stop speaking out on topics he feels strongly about when he becomes king, as he is “not that stupid”.
He has campaigned on issues such as the environment for decades, but says he would not do the same as monarch.
Speaking in a BBC documentary to mark his 70th birthday, Prince Charles said the idea that he would continue making interventions was “nonsense”.
He said he would have to operate within “constitutional parameters”.
In the hour-long programme, he was asked about what some people have called his “meddling”, but said he had always tried to remain “non-party political”.
He said: “I think it’s vital to remember there’s only room for one sovereign at a time, not two.
“So, you can’t be the same as the sovereign if you’re the Prince of Wales or the heir.
“But the idea, somehow, that I’m going to go on in exactly the same way, if I have to succeed, is complete nonsense because the two – the two situations – are completely different.”
Asked whether his public campaigning would continue, he said: “No, it won’t. I’m not that stupid.
“I do realise that it is a separate exercise being sovereign. So of course I understand entirely how that should operate.”
Documentary film maker John Bridcut, who followed the royal for 12 months, said Prince Charles “bridled a bit” at the use of the word meddling, and instead preferred to think of his interventions as “motivating”.
The heir to the throne said: “If it’s meddling to worry about the inner cities as I did 40 years ago, then if that’s meddling I’m proud of it.”
BBC royal correspondent Nicholas Witchell said there would be “some relief in Whitehall” that the prince had publicly recognised how different his role as sovereign would be.
He added they were “comments of real significance” – although the prince had not entirely ruled out using his convening powers to bring people together, potentially for conferences on the environment and other topics.
But Prince Charles acknowledged “he could only do that with the agreement of ministers”, our correspondent said.
Mr Bridcut said: “People who think he’s hanging around, longing to be king, are very mistaken.
“It’s not something he’s dying to assume because inevitably it will only arise after the death of his mother. “
He added that the Duchess of Cornwall, who is also interviewed in the documentary, “makes the point that this burden does not weigh heavily on his shoulders”.
The BBC has been given exclusive access to film Prince Charles, who turns 70 on 14 November.
Also appearing on the programme, the Duke of Cambridge said he would like his father to spend more time with his grandchildren – Prince George, Princess Charlotte and Prince Louis.
Prince William said, “when he’s there, he’s brilliant” but “we need him there as much as possible”.
‘People on his side’
By Roger Harrabin, BBC environment analyst
The prince warned decades ago about human-induced climate change. It was controversial to some at the time, but now there’s scientific consensus on the threat.
On wildlife he rightly predicted a huge loss of species. He campaigned against rainforest destruction, and he’ll be pleased at the recent focus on the impact of farming on forests, and therefore on the climate.
His concern for soil sounded dotty to some observers, but it’s now acknowledged that many areas face a crisis of soil degradation and loss.
On these matters, the mainstream has flowed towards the future monarch.
On GM crops, the prince remains in conflict with the scientific establishment.
On other hobby horses, such as homeopathy and architecture, he has expressed opinion rather than fact – but still he’ll have some people on his side.
- Prince, Son And Heir: Charles At 70, will be screened on BBC One on Thursday 8 November at 9pm.