Charles, 9th Earl Spencer, regularly delights his social media followers with his fascinating insights about his home, Althorp House, and old family photographs.
On Monday, the author recalled an important historical anniversary about one of King Charles III's predecessors.
Sharing an image of his book, Killers of The King: The Men Who Dared to Execute Charles I, the Earl wrote on Twitter: "Today's the 1649 anniversary of the execution of Charles I. His killers were mainly tough Parliamentary army officers, & religious (some fanatically so) men who thought the royal execution might end years of bloody civil war. Charles was supremely brave & dignified at his end."
The Earl marked a historical event on Monday
Charles I ascended the throne in 1625 and during his reign, his actions resulted in the English Civil War, eventually leading to his execution in 1649.
He was succeeded by his son, Charles II, in 1660, following the death of Oliver Cromwell.
GALLERY: Inside Charles Spencer's relationship with Prince William and Prince Harry
© Photo: Getty ImagesEarl Spencer is custodian of Althorp House
The current King could have chosen a different regnal name but opted to go down the same route as his late mother, Queen Elizabeth II, and retain his moniker to become Charles III.
It is not known yet whether Earl Spencer will be included on the guestlist for his former brother-in-law's coronation on 6 May at Westminster Abbey.
Charles was among those to pay their respects to the late Queen Elizabeth II at her commital service in Windsor last September.
He has remained close to his nephews, Prince William and Prince Harry, since the death of their mother and Charles's sister, Princess Diana, in 1997.
The Earl has been custodian of Althorp House in Northampton since the death of his father, John, 8th Earl Spencer, in 1992. He regularly shares snapshots and videos from his stunning residence, as seen in the video below.
WATCH: Charles Spencer's family home revealed
The Grade I listed residence where the late Princess Diana grew up has 90 spectacular rooms and is surrounded by 550 glorious acres of land. The Northamptonshire estate is also the royal's final resting place.
LISTEN: King Charles - The Man Under The Crown
Make sure you never miss a ROYAL story! Sign up to The Royal Explainer newsletter to receive your weekly dose of royal features and other exclusive content straight to your inbox.
