Prince Harry has been vocal about environmental issues for several years now, but he was a cleanliness advocate even when he was a child. The royal was even mocked at school for his habit of picking up rubbish that he spotted on the campus or roads.

He picked up the habit from his father Prince Charles, who would always encourage him and his elder brother William to pick up litter whenever they were out and about. So whenever Harry was out walking, he could not resist picking up the litter that didn't belong there, reports The Mirror.

Harry made the revelation several years ago in a documentary titled "Prince, Son and Heir: Charles at 70." He admitted, "I used to get taken the mickey out of at school for just picking up rubbish. I don't go consciously looking for it. When you go for walks anywhere, if you see something, it stands out, you pick it up."

"It's like I've literally done this because I'm programmed to do it, because my father did it. Actually, we should all be doing it," he added.

Harry's nephew Prince George has also picked up the same habit from his elder family members. Prince William revealed last month that his eight-year-old son had become "a bit confused and annoyed" at the state of the planet during litter picking sessions when he found the route he cleaned became littered the next day 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?'" the Duke of Cambridge told BBC Newcast podcast.

Apart from litter picking, there's another environment-friendly habit that has been programmed into William and Harry by their father. They revealed in the same documentary that they are all obsessed with turning the lights off.

Harry said, "He's a stickler for turning lights off. And that's now something that I'm obsessed with as well, which is insane because actually, my wife goes 'Well, why turn the lights off? You know it's dark.' I go 'we only need one light, we don't need like six,' and all of a sudden, it becomes a habit and those small habit changes he's making, every single person can do."

Princess Diana
14 July 1986: Prince Charles and Princess Diana hold their sons Prince William and Prince Harry in the wildflower meadow at Highgrove Tim Graham/Getty Images