Fresh details have emerged surrounding the royal family's finances and private estates in a new investigation carried out by Channel 4's Dispatches and the Sunday Times.
Their investigation claims that King Charles and Prince William's private estates - The Duchies of Lancaster and Cornwall - have received millions of pounds of income from contracts with public bodies and charities.
It claims that these deals with the Duchies are set to make at least £50 million in the coming years.
The Duchy of Lancaster is a portfolio of land, property and assets across England and Wales held in trust for the Sovereign, including key urban developments, historic buildings, high-quality farmland and areas of great natural beauty, dating back to the 14th century.
The Duchy of Cornwall is a similar portfolio valued at more than £1 billion, providing an income for the heir to the throne.
Both estates are exempt from paying Corporation Tax or Capital Gains Tax. Neither the King nor the Prince of Wales are legally required to pay income tax on what they receive from the Duchies, but both voluntarily do so.
Keep scrolling to discover some of the documentary's biggest claims…
Properties rented out by both duchies are in breach of basic government energy efficiency standards
Working with the Mirror newspaper, the investigation found that private residential properties rented out by both duchies fail to meet minimum energy efficiency requirements.
It reported that 14% of homes leased by the Duchy of Cornwall and 13% by the Duchy of Lancaster have a performance rating of F or G, despite it being against the law for landlords to rent out properties rated below an E since 2020.
Responding to the claims, a Duchy of Lancaster spokesperson said: "The Duchy of Lancaster operates as a commercial company, managing a broad range of land and property assets across England and Wales. It complies with all relevant UK legislation and regulatory standards applicable to its range of business activities."
They continued: "The Duchy has made a number of key environmental improvements in recent years, delivering a significant increase in the number of A+, A and B EPC ratings awarded to our properties as a result of refurbishment or restoration works.
"Currently, over 87% of all Duchy let properties are rated E or above. The remainder are either awaiting scheduled improvement works or are exempted under UK legislation."
King Charles and Prince William 'making millions' from charities and public services
The investigation alleges that the Duchy of Cornwall has pocketed at least £22 million since 2005 from a share of rents paid on Camelford House. The documentary also claims that St John's Ambulance - for which Charles is a patron - previously paid the Duchy of Cornwall almost £60,000 for use of its land.
Beyond this, the investigation claims that the Duchy of Cornwall charges the RNLI small amounts to use slipways in the South West.
Elsewhere, the Channel 4 Dispatches documentary also alleges that the Duchy of Lancaster is receiving £11.4 million as part of a deal with Guy's and St Thomas' NHS Trust to store its fleet of electric ambulances in a warehouse owned by the Duchy of Lancaster.
It also claims that William's Duchy of Cornwall has signed a £37 million deal to lease Dartmoor prison for 25 years to the Ministry of Justice.
Controversial mining on duchy land
While King Charles and Prince William are both environmental advocates, the Dispatches investigation detailed that the Duchies have struck up deals with controversial mining companies for sites across the country.
The Duchy of Cornwall allegedly leases land to one of the biggest polluters in Europe.
In response to the investigation, a Duchy of Cornwall spokesperson said: “The Duchy of Cornwall is a private estate with a commercial imperative which we achieve alongside our commitment to restoring the natural environment and generating positive social impact for our communities.
"Prince William became Duke of Cornwall in September 2022 and since then has committed to an expansive transformation of the Duchy. This includes a significant investment to make the estate net zero by the end of 2032, as well as establishing targeted mental health support for our tenants and working with local partners to help tackle homelessness in Cornwall."
HELLO! has reached out to Buckingham Palace for comment.