As members of one of the most privileged families on earth, the Prince of Wales could have taken his sons virtually anywhere on their family holidays.
Instead, the Dukes of Cambridge and Sussex have disclosed, he taught them how to have a good time in outings to the Norfolk countryside, picking litter.
The brothers have told how their father took them out to pick up rubbish, equipping them with poles and black bin bangs to instill their love of the environment.
The Duke of Sussex said the habit was so ingrained that he endured teasing at school for picking up stray litter when out with friends.
In a television interview in honour of the Prince of Wales’ 70th birthday, Prince William and Prince Harry spoke affectionately about their father, highlighting how he was ahead of his time in making speeches about the perils of plastic on the environment.
“He’s done an amazing job,” said the Duke of Sussex. “Without telling us what we should be doing or the direction we should go in, 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 taken the mickey out of at school for picking up rubbish. I didn’t go out consciously looking for it but when you go for walks anywhere and you see something and it stands out, you pick it up.
“And before you know it someone is like ‘what are you doing? Where are you going to put that?’ It’s like wow, I’ve literally done this because I’m programmed to do it because my father did it. We should all be doing it.”
An Image of Prince Charles from Prince, Son and Heir: Charles at 70 Credit: Hugo Burnand
The Duke of Cambridge added: “He took us litter picking when we were younger, on holiday. We were in norfolk on school holidays and we went out litter picking with him.
“We thought this is perfectly normal, everyone must do it. We were there with our spikes stabbing the rubbish into black plastic bags.”
On the topic of speaking out about the environment and climate change while flying around the world by polluting plane, Prince William added: “He does live the way that he advocates. Until someone comes up with an electric plane, it’s impossible to get around the world without using a plane that’s there.
“He did take the criticism to heart quite a lot when he was younger.”
On Saturday, as the Prince of Wales visited Ghana, he saw a glimpse of the problem of plastics in the ocean at a beach outside Christiansborg Castle, where he was given a tour of the historic building.
Built in 1661, it was once a fort owned by the Danes and used to keep slaves awaiting trafficking to the New World.
In a poignant moment, the Prince walked down the spiral staircase once used by slaves walking to dungeons where they were held for up to six months, pausing at the “Door of No Return” which saw them walk out onto the beach and on board waiting ships.
The castle later went on to be the headquarters of the British colonial government, then a seat of Ghanaian government after its declaration of independence, and is now being transformed into a museum to tell visitors its history by architect Sir David Adjaye.
After the visit concluded, the Prince was persuaded to join an impromptu dance party today, as he was handed a small Ghanaian percussion instrument to take a starring role in a local band waiting outside.
Presented with a calabash, a small instrument not unlike the maracas, he gamely shook it in time with the music as he danced along, to the delight of locals in Osu.
In the afternoon, joined by the Duchess of Cornwall visited Jamestown in Accra, for an event celebrating youth culture, music, art, sport and heritage.
In the 31C humidity, the Duchess used her brightly-coloured hand-held fan to cheerfully bat away stray footballs which kept flying towards them.
On Sunday, they will fly to Kumasi, also in Ghana, to see a spectacular durbar, a ceremony paying homage to leaders, and have tea with The Asantehene.
The documentary, Prince, Son And Heir: Charles At 70, will be broadcast on Thursday, November 8 on BBC One at 9pm.