LONDON - The heir to the British throne, Prince Charles, has said in a birthday interview he won't be a meddling king when he replaces his mom, Queen Elizabeth II.

Charles, who as the monarch's eldest son is the Prince of Wales, is about to celebrate his 70th birthday on Nov 14, and made the comment in a media interview.

He has a reputation of making his views known on a range of subjects ranging from architecture, the environment, climate change to natural health remedies such as homeopathy.

In a documentary for the BBC, the prince said he will stop speaking out on topics he feels strongly about when he becomes king, adding that "he is not that stupid".

Prince Charles said the idea he would continue making interventions as king was nonsense, adding he would have to operate within constitutional parameters.

Queen Elizabeth never comments on political matters, though what she says at her regular meetings with serving prime ministers is never reported or publicly disclosed.

According to the BBC, in the documentary, Prince Charles was asked about his campaigning, which some people described as "meddling".

Documentary film-maker John Bridcut, who followed the prince 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."

He added the roles of Prince of Wales and king were completely separate.

There is media speculation in Britain that at some time in the next year or so Queen Elizabeth, 93 next birthday, will retire from public duty, with her son taking over as Prince Region. That would give him all of the powers of a monarch, but not the title of king while his mom is still alive.

The Queen's husband, Prince Philip, the Duke of Edinburgh, has already retired from public life.

Royal watchers say Queen Elizabeth will never abdicate, and would retain the title of Queen should she hand over to Charles.

Bridcut told the BBC: "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."

As the Queen reduces her workload, more of her official duties are being carried out by her grandchildren and their wives, William and Catherine, the Duke and Duchess of Cambridge, and newly-weds Harry and US actress Meghan, the Duke and Duchess of Sussex.