Prince Charles has denied suggestions he'll be a meddling monarch when he one day becomes king, saying "I'm not that stupid".
The Prince of Wales has given his most open interview in recent years about how he sees the role of monarch compared to that of being heir to the throne, as part of a documentary to mark his 70th birthday next week.
In the programme Prince Charles is asked how he sees the two roles as being different. The Prince says: "I've tried to make sure whatever I've done has been non party political.
But 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.
"Clearly, I won't be able to do the same things I've done, you know, as heir so of course you operate within the-, the constitutional parameters."
But when the interviewer suggests that some people are concerned his involvement will continue in the same way, Prince Charles becomes more animated, and replies in a direct way, saying: "No, it won't. I'm not that stupid, I do realise that it is a separate exercise being sovereign. So of course, erm, you know I understand entirely how that should operate."
Over the past 50 years the Prince has become well known for his strong views on issues such as climate change, the environment, architecture and support for young people.
Applauded by some for his dedication and campaigning spirit, he has been criticised by others for trying to influence government policy.
When it is put to the Prince that some people see him as meddling, he replies: "Really? You don't say. But I always wonder what meddling is, I mean I always thought it was motivating."
The BBC documentary Prince, Son & Heir : Charles at 70, was given exclusive access to the Prince of Wales and his family over the past 12 months in the run up to his 70th birthday next week on the 14 November.
As well as showing his official work there are funny moments, as he's seen talking to turkeys on his Dumfries House estate, or going on an impromptu shopping spree in a market in Vanuatu, which leaves his team desperately trying to find local currency to pay for his purchases.
The programme also features interviews with those closest to the Prince. The Duchess of Cornwall pays tribute to her husband saying that she wishes people got to know him better and his sense of humour.
She says: "He's a very exceptional man. They see him as a very serious person, which he is. But I would like a lot of people to see the lighter side of him."
Asked what advice she would like to give him for his 70th birthday she adds: "My Father once said to me, 'As you get older, you've got to do one thing and that is pace yourself. And I would love to tell him to pace himself, but I'm afraid that's not gonna happen."
Prince Harry explains how grateful he was to his father for stepping in to walk his wife Meghan down the aisle on their wedding day.
He says: "I asked him to and I think he knew it was coming and he immediately said 'yes, of course, I'll do whatever Megan needs and I'm here to support you'.
"For him that's a fantastic opportunity to step up and be that support, and you know he's our father so of course he's gonna be there for us."
Prince William talks about wanting his father to spend more time with his grandchildren saying: "Now he's reached his seventieth year it's a perfect time to consolidate a little bit 'cause as most families would do, you are worried about having them around and making sure their health's okay, and he's the fittest man I know but equally I want him to be fit until he's 95 you know going on.
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"So, having more time with him at home would be lovely, and being able to you know play around, er, with the grandchildren. 'Cause when he's there, he's brilliant. Er, but we need him there as much as possible."
:: Prince, Son & Heir : Charles at 70 will be shown on BBC One at 9pm tonight.