But Charles defended his past actions, including establishing the Prince's Trust in 1976 to help disadvantaged young people, saying he had always steered clear of party politics. "Not two", he says.
Anti-monarchy campaigners Republic have claimed that tonight's BBC documentary marking the Prince of Wales" 70th birthday is just a "rushed' PR exercise to boost his popularity. So, of course, you operate within the constitutional parameters. "You only have to look at Shakespeare plays, "Henry V" or 'Henry IV, Part 1 and 2, ' to see the change that can take place - because if you become the sovereign, then you play the role in the way that it is expected", he said.
"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. I was very grateful for him to be able to do that". "But it's a different function".
Charles has attracted criticism for decades over his outspoken views and his private communications with government ministers on issues close to his heart, including the environment, GM crops, sustainable agriculture, organic farming, architecture and climate change.
After Meghan Markle's father Thomas announced he was unable to attend due to health concerns, Prince Harry says he asked his dad to do the honours, and he immediately said "yes". "I don't think people realise quite how kind he is". "So, of course, you know, I understand entirely how that should operate".
Charles' wife, Camilla, agrees that she thinks the heir to the throne is fantastic with children, mentioning her own four grandchildren from her previous marriage. But William adds that they all want more time with Charles who has a packed royal agenda even as he approaches seventy. Because when he's there, he's brilliant.
Prince, Son and Heir: Charles will be streamed live on the BBC website, and will also be available for a limited time on BBC iPlayer afterwards.
Prince Harry and Meghan Markle are expecting their very first addition to the family, and now, a report claims the Royals are planning to give their offspring a normal upbringing - at least as much as possible!