The childhood story that speaks volumes about what Prince Charles is like as a father.

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Written with AAP.

Giving us a rare insight into Prince Charles as a parent, Prince Harry and Prince William have described a heartwarming habit they unconsciously picked up from their parent.

Sharing the anecdote in a BBC film, Prince, Son and Heir: Charles at 70, made to commemorate Charles’ 70th birthday on November 14, it’s evident that Prince Charles taught his children the importance of the environment by taking his teenage sons out to pick up rubbish.

“We were in Norfolk on school holidays, and went out litter-picking with him … Both of us thought, ‘This is perfectly normal, everyone must do it,'” shared Prince Harry who is currently expecting his first child with wife, Meghan Markle.

“We’re there with our, basically, spikes, stabbing the rubbish into black plastic bags.”

Harry added that he was "programmed" to pick up rubbish by his father, and joked that it resulted in him getting teased at school.

"He's just let us learn from the nature of the job, 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 shared.

Growing up royal with Prince William and Harry. Post continues after video. 

Despite this, he only had glowing things to say about Prince Charles' parenting, and said he had "done an amazing job" as a father "without telling us what we should be doing or what direction we should be going".

Also praising his dad, Prince William said his father was affected by the backlash he received for his well-established environmental views. The 69-year-old is known to be a advocate for climate protection and threatened species, as well as his interests in organic farming.

Controversially, he was once quoted as saying that he enjoyed talking to plants, something he was inevitably ridiculed for.

"He does live the way he advocates so, until someone comes up with an electric plane - it's impossible to get round the world, for instance, without using a plane that's there," he said.

"He did take to heart the criticism quite a lot when he was younger."

Although we don't know a lot about the parenting dynamic between Prince Charles and his two sons, speculation around their relationship hasn't always been positive.

However, given the recent footage of Prince William and Prince Harry speaking of their father, we're not sure if this is true.

What do you think of this insight into Prince Charles' parenting techniques? Tell us in a comment below.