The day Charles took Prince William and Prince Harry 'litter picking' in Norfolk

Prince William said his father lives 'the way he advocates' when it comes to his strong environmental beliefs and Harry said he was programmed' to collect litter. Photo / Getty Images

Princes William and Harry have revealed that Prince Charles once took them to pick up litter during a holiday in Norfolk.

The Prince of Wales, well known for his fervent interest in environmental causes, gave his sons steel spikes and black plastic bags and set them to work, reports The Daily Mail.

"He took us litter picking... Both of us thought, 'This is perfectly normal, everyone must do it'.

"We're there with our spikes stabbing the rubbish into black plastic bags," Prince William tells a BBC documentary to mark Charles's forthcoming 70th birthday.

He adds that his father lives "the way he advocates" when it comes to his environmental beliefs.

In the film, the brothers watch a recording of Charles giving a remarkably prescient speech in 1970 in which he mentions the problems presented by an increasingly throwaway plastic society.

William admits that his father was affected by the backlash he received for his environmental views, which saw him ridiculed for supposedly talking to plants.

Harry confesses that he was 'programmed' to collect litter because of the positive influence of his father.

"He's just let us learn… from him, learn from Mummy, to the point where I used to get the… mickey [taken] out of me at school for just picking up rubbish," he says.