Often characterised as 'work-shy' and reluctant to undertake the vast number of engagements carried out by members of the Royal Family decades his senior, Prince William will have surprised some people with one particular piece of news this week.

Not his unfettered celebrations in Istanbul with some of his oldest friends - as Aston Villa, the football team he so passionately supports, won the Europa League, their first major trophy in 30 years.

No, it was the announcement that the heir to the throne would sell off a fifth of the Duchy of Cornwall, the £1billion estate which he inherited after his father became King in 2022.

The sell-off will happen over the next ten years, as William plans to invest £500million in tackling the crises in nature and housing.

Will Bax, chief executive of the duchy, said the future king would consolidate his holdings around five geographic 'heartlands' - focusing on Dartmoor, Cornwall, the Isles of Scilly, the Bath area and Kennington, south London - where he felt he could make the greatest environmental and social impact.

The prince decided that the duchy 'shouldn't exist to just own land. It should first and foremost exist to have a positive impact on the world', Bax said.

William's move ties in with his decision to focus on two areas where he feels he can make a difference to the world: the environment and the scourge of homelessness.

When King Charles was the Prince of Wales, he was criticised for making endless 'doom and gloom' speeches about the environment which could leave people with the feeling of helplessness. Who can forget how Charles warned in March 2009 that humanity had 'less than 100 months' to save the planet from catastrophic climate change? Two hundred and four months later, the catastrophe does not seem to have happened - and people have become wary of such alarmism.

William realised this and, wisely, has instead concentrated his efforts on trying to encourage practical efforts to improve the environment. In 2021, he launched The Earthshot Prize, a global scheme that awards five winners each year for their contributions towards improving the planet. Each winner receives a grant of £1million to continue their environmental work.

His work to end homelessness is similarly based on practical action not pontificating. In 2023, he created Homewards, a project 'to demonstrate that it is possible to make homelessness rare, brief and unrepeated'. Designed to be transformative, the five-year programme was based in six flagship locations around the UK, with up to £500,000 of funding provided by his and his wife's charity, the Royal Foundation, for each location.

No one will have read William's announcement this week more closely than the Duke of Sussex, who was always envious of his brother's position of heir to the Duchy of Cornwall and future king.

Prince Harry and Meghan quit official duties to seek a fortune across the Atlantic before attacking the Royal Family at every opportunity. Despite this, King Charles has declined to take any action against his son and daughter-in-law.

He has allowed Harry to retain his position, fifth in the line of succession. He has also permitted the pair to keep their Duke and Duchess of Sussex titles, even though they regularly use them in their commercial activities, in apparent defiance of the agreement made with the late Queen Elizabeth at the 'Sandringham summit' in 2020.

Even more generously, the King has allowed Harry to remain a Counsellor of State, meaning that he could, in theory at least, stand in for the monarch if Charles was unable to carry out his duties because of illness.

'William will take a much harder line with Harry and Meghan when he's king,' predicts one of his friends, who declines to spell out exactly what that will mean for the California-based couple.

What we can deduce from this week's radical announcement about the Duchy of Cornwall - as well as his intense display of emotion at the Aston Villa game in Istanbul - is that William will be different. And that whatever action he takes against the Sussexes, it will be dramatic.

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