The family spent an hour and a half with volunteers from the Marine Conservation Society in Portsmouth, where they collected rubbish from Southsea beach alongside a local beach cleaning group.
While both children were keen to help their parents' environmental efforts, they also made time to have fun and tease each other, with James prodding the back of his sister's legs when they were both given grabbers for the litter pick.
WATCH: The Earl and Countess of Wessex took their children out for a very special reason
Later, Louise laughed at her brother when James was initially given two left-handed gloves. "I knew there was something wrong with you," she joked.
The 16-year-old shared her enthusiasm with the press about starting her A-Levels in English, history, politics, and drama, and also spoke about the increase in plastic waste during the coronavirus pandemic.
The royal couple and their children helped local volunteers
The teenager said: "Everything has got worse this year because everyone has gone back to non-reusable, non-recyclable plastic cups."
Her mother, meanwhile, who looked casual but stylish in jeans, a loose top, and white Tom's espadrilles, expressed her concern over the lack of recycling options for PPE, especially face masks.
Speaking about the fact that the public needs more information about how best to dispose of them, Sophie said: "The medical profession, they know what to do, [but] there is no information about how people should dispose of them."
She went on: "Obviously we would want to encourage people to use these lovely reusable masks, but sometimes you can’t. It’s so difficult because councils are stretched at the moment."
The Countess shared that she tries to do her part close to her home to help remove unsightly litter.
The family is enthusiastic about helping the environment
She said: "We are lucky enough to live next door to a lovely forest, and I come back with handfuls of litter every time we go for a walk."
Asked about her children's reaction to this, she admitted: "They are always going, 'Oh no Mummy, not again!' and off I go into the bushes to get something else."
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