Speaking during ITV programme The Royal Restoration back in 2012, His Majesty spoke about the £20 million loan he took out to restore Dumfries House in Ayrshire back in 2007.
The decision was intended to save the house's furniture from being sold off, and saw the royal take out a loan from his own charitable foundation.
WATCH: Queen Consort Camilla reveals how Queen reacted to wedding mishap
Although his move received some initial criticism, the father-of-two paid back the money by the time of his interview with Alan, as well as raising an additional £11 million.
Asked about the project by the interviewer, the-then Prince of Wales responded: "You have got to get stuck in and try to make a difference."
King Charles unveils a knitted art installation at Dumfries House
His £1.2billion Duchy of Cornwall holdings now belong to his eldest son Prince William, who has become the biggest private landowner in Britain.
The Duchy of Cornwall spans across 23 counties and includes housing developments, castles and commercial property, as well as some more surprising acquisitions – from a prison to a cricket ground, and of course, Charles' much-loved Highgrove estate.
His Majesty and the late Queen photographed at Birkhall
The property has been described as "a unique haven of cosiness and character" by the King himself, and is where he and his wife spent some of their honeymoon following their wedding in 2005.
It is also where the royal couple isolated during the first coronavirus lockdown in 2020.
Make sure you never miss a ROYAL story! Sign up to our newsletter to get all of our celebrity and royal news delivered directly to your inbox.