Britain's Prince Charles has never changed his grandchildren George or Charlotte's dirty nappies.

Prince Charles

Prince Charles

The 68-year-old royal - the eldest son of Queen Elizabeth and Prince Philip - has admitted he "comes alive" when he's around his son William and daughter-in-law Catherine's little ones but can't bring himself to change their smelly bottoms.

The heir-to-the-throne made the revelation as part of his forthcoming TV documentary 'When Ant and Dec Met the Prince: 40 Years of the Prince's Trust', but when on to say he's incredibly grateful for George, two, and seven-month-old Charlotte as he hopes they'll look after him in the future.

He said: "[They will] look after me when I'm tottering about."

Meanwhile, the forthcoming programme promises to reveal a different side to Charles as he gives a glimpse into his life as a father to William, 33, and Harry, 31, as well as his marriage to his second wife Duchess Camilla, 68.

Presenting duo Ant McPartlin and Declan Donnelly - known also as Ant and Dec - said of their interview with Charles: "He was lovely about Camilla and the two boys and being a granddad. It was fascinating just to hear him talk like that."

The 90-minute documentary also features Prince William and Prince Harry and sees them speak at length to Ant and Dec about their father and recall stories from their youth, and the influence he's had on them now they're adults.

'When Ant & Dec Met the Prince: 40 Years of the Prince's Trust' will air on January 4 at 9pm on ITV.