Prince Charles is one proud grandfather. The heir to the throne was delighted to inherit the name upon the birth of Prince George in 2013 and even more so when Prince William and Kate welcomed their first daughter, Princess Charlotte, in May. And the royal always jumps at the chance to spend time with his grandchildren, even sharing his love for gardening with George, who helped him plant two new trees in the gardens of Highgrove.

SCROLL DOWN FOR VIDEO

Prince Charles has revealed he has never changed George or Charlotte's diapers. Photo: © Getty Images

While the future King loves the company of his grandchildren, there's one task that he isn't so keen on – changing diapers.

In a new documentary, When Ant and Dec Met The Prince: 40 Years of the Prince's Trust, which will air Jan. 4 in the U.K., the Prince of Wales admits "with the merest hint of a blushed cheek" that he hasn't yet changed any diapers. The royal added that he is thankful that he will have them "to look after me when I'm tottering about," reports Event magazine via Daily Mail.

Prince Charles and Prince George planted several trees in the gardens of Highgrove earlier this year. Photo: © Getty Images

The comedy duo sat down with the prince to talk about the 40th anniversary of the Prince's Trust and his relationship with his grandchildren.

"He was lovely about Camilla and the two boys and being a granddad," recalls Ant McPartin. "It was fascinating just to hear him talk like that."

Here’s a sneak peek of when @antanddec met The Prince. #TrustAt40https://t.co/WApmmPgJfN

— Clarence House (@ClarenceHouse) December 28, 2015

Princes William and Harry were also interviewed for the special occasion and talked about their love and respect for their "incredibly hard-working" dad. Charles's sons also revealed how he used to embarrass them, laughing in all the wrong places at their school plays.

Their father would also send the young princes hand-written notes so indecipherable that they would have to pass them between each other to work out if they were being praised or told off.

Prince William and Kate released a new family portrait earlier this month. Photo: © Getty Images

The special's director is Bafta-winning producer Michael Waldman, who also made the documentary Our Queen to mark the Diamond Jubilee in 2012.