The palace has always sought to crush rumors that Prince Charles does not get to see much of his grandson Prince George, and have long rebuked well-sourced stories that Charles is jealous of the huge input the Middleton family gets into the lives of the monarchy’s youngest generation.

Now, however, in a new interview to mark Charles’ 70th birthday, comes a careful admission from Prince William that Charles does not spend a large amount of time with his grandchildren.

Three years ago, it was reported that Charles complained that he “almost never” sees Prince George, and was said to have told friends that he occupied little more than a peripheral role in his life.

The palace pushed back hard against those stories, but now there’s an admission, of sorts, that there was some truth in them, with William saying, “When he’s there, he’s brilliant. But we need him there as much as possible.”

The interview forms part of a 60-minute documentary to be shown this week in the U.K. that is widely being seen as laying the groundwork of public opinion for his accession to the throne. In the film, Charles promises to stop “meddling” and proffering opinions on outside issues, saying, “the idea somehow that I’m going to go on exactly the same way, if I have to succeed, is complete nonsense.”

William is asked directly about the amount of time Charles spends with his grandchildren and replies: “It’s something I’m working more heavily on, put it that way. I think he does have time for it, but I would like him to have more time with the children.

“Now he’s reached his 70th year, it’s a perfect time to consolidate a little bit because, as most families would do, you are worried about having them around and making sure their health’s OK—and he’s the fittest man I know, but equally I want him to be fit until he’s 95.

“So having more time with him at home would be lovely, and being able to play around with the grandchildren. 

“Because when he’s there, he's brilliant. But we need him there as much as possible.”

There is a concerted effort to portray Charles as a doting grandpa, with Camilla saying: “He will get down on his knees and crawl about with them for hours, you know making funny noises and laughing, and my grandchildren adore him, absolutely adore him. He reads Harry Potter and he can do all the different voices and I think children really appreciate that.”

Charles’ exclusion from the family life of his grandchildren was highlighted after the birth of Prince Louis.

The first visitors to Kensington Palace were all Middletons, led by Kate’s mother Carole, her sister Pippa, father Michael, and brother James.