When the Queen joked that her first-born son was a “true Duchy Original” during his 70th birthday party, it raised a hearty laugh from friends, family and royal watchers but required a little explaining to some in the wider world.
But anyone who has wondered what exactly the Duchy of Cornwall is and does, not to mention how it funds the lives of the Prince of Wales and his children, will soon be wondering no more.
The Prince has allowed television cameras into film the inner workings of his Duchy, with a crew embedding for a year behind-the-scenes to shed light on the royal estate.
Including interviews with the Prince himself, it will follow staff and tenants working and living across the 700-year-old estate which now creates £20million a year for its custodian and his charities.
The ITV television programme, which will be aired in two one-hour documentaries, will be broadcast in the autumn, after the Prince celebrates his 50th working year as the Duke of Cornwall.
Provisionally called Inside The Duchy, it will see the Prince explain “the way The Duchy is run to reflect his belief that economic development works best when in harmony with the natural world and local communities”, a spokesman for ITV said.
The Prince has been highly selective about which television projects he takes part in personally, with a CV now including a guest editing slot on Countryfile in 2013 and a recent and revealing BBC documentary marking his 70th birthday.
The new programme is intended to focus closely on the work of the Duchy, joining the Prince in meetings, at his Poundbury housing estate and out in the countryside.
Fittingly, he has been filmed laying a hedge: one of his passionate hobbies which his sons Prince William and Prince Harry have laughingly described as causing his policeman to come back from work bleeding after helping him.
The Duke of Cambridge, who will one day take over the estate, could make an appearance on screen, having attended regular meetings about the Duchy recently.
ITV said the programme will “offer an unprecedented insight into The Duchy of Cornwall, which covers more than 130,000 acres across 23 counties, touching coast, countryside and city.”
“This unique 700 year old institution is both an ancient Royal estate, providing the personal income for every Duke of Cornwall since 1337, and a forward-thinking 21st century business, generating an income of over £20 million per year for The Prince, his family and his charitable organisations,” a spokesman added.
In particular, the estate currently funds the staff and lives of the Prince of Wales and Duchess of Cornwall, the Cambridges and the Sussexes, with the exception of security and working travel.
A royal source said it was hoped that the documentary would help explain to the public how the Duchy “not only makes a positive contribution to communities where it has land and investments, but also significantly contributes to the costs of the Prince’s household and those of his children”.
Bill Lyons, the executive producer who has also worked on programmes including Countryfile, said: “It’s rare to have access to an untold story but that’s exactly what we discovered in the Duchy of Cornwall.
“These films will reveal just how much HRH The Prince of Wales has invested - personally and emotionally - into what has been his lifetime’s endeavour.”
Jon Swain, head of BBC Studios’ Unscripted Productions which will make the show for ITV, said: “We’re delighted to be working with ITV and opening a window onto one of the world’s most extraordinary family businesses.”
The Duchy estate was established by Edward III to provide a private income for his son and heir to the throne Edward, later known as the Black Prince, and its purpose remains the same today.
Prince Charles became the 24th Duke of Cornwall on the Queen's accession to the throne in 1952 and at the age of 21, in 1969, he became entitled to the full income from the Duchy and took over its management.
Today it is a private portfolio of land, financial investments and property - including the Oval cricket ground and 67,000 acres of Dartmoor - which funds the public, charitable and private activities of the prince and his immediate family.
The 2017/18 accounts for the Duchy showed annual income from the private estate had increased by 5 per cent to £21.7 million.