Prince George has been litter picking at school but is "confused" and "annoyed" that the rubbish keeps reappearing, the Duke of Cambridge has revealed.
Prince William said his eight-year-old son, who is in Year 4 at Thomas's Battersea prep school, could not understand why the litter he was clearing up was not going away.
Speaking to BBC Newscast on BBC Sounds, ahead of the inaugural Earthshot Prize award ceremony on Sunday, he also warned that it would be an "absolute disaster" if the young Prince was forced to follow in his footsteps and campaign about environmental issues in 30 years' time, when it would be too late.
He said: "So George at school recently has been doing litter picking, and I didn't realise but talking to him the other day he was already showing that he was getting a bit confused and a bit sort of annoyed by the fact they went out litter picking one day and then the very next day they did the same route, same time and pretty much all the same litter they picked up back again.
"And I think that for him he was trying to understand how and where it all came from. He couldn't understand, he's like, well, we cleaned this. Why has it not gone away?"
Earthshot Prize will 'stimulate solutions'
The Duke expressed frustration that despite environmental campaigns by both his grandfather, the Duke of Edinburgh's generation as well as his father's, the planet was still in crisis.
"It shouldn't be that there's a third generation now coming along having to ramp it up even more," he said.
"And you know, for me, it would be an absolute disaster if George is sat here talking to you or your successor, Adam, you know in like 30 years' time, whatever, still saying the same thing, because by then we will be too late."
He said his father, the Prince of Wales, had endured "a really rough ride" in campaigning for the environment but had been "proven to be well ahead of the curve" with his early warnings about climate change.
The 35-minute interview, recorded at Kensington Palace, saw the Duke express his concerns about a range of issues related to the environment.
He said he hoped the Earthshot Prize, a £50 million initiative aiming to promote and fund innovative ways to repair the planet, will "stimulate solutions and action that a lot of people haven't necessarily produced yet".
"I'm hoping, you know, the prize will galvanise a lot of people in positions of responsibility to, you know, go further, bigger and actually start to deliver," he added.
He said that as a parent, like others, he had started to see the world differently.
"I want the things that I’ve enjoyed – the outdoor life, nature, the environment – I want that to be there for my children, and not just my children but everyone else's children," he said.
"If we're not careful we're robbing from our children's future through what we do now. And I think that's not fair."
The Duke added: "We are seeing a rise in climate anxiety. You know, people, young people now are growing up where their futures are basically threatened the whole time. It's very unnerving and it's very you know, anxiety making."