Prince William made a private visit to London’s MI6 headquarters on Thursday — but details of his visit are being kept hush-hush.

The Prince of Wales, 41, met with the British Secret Intelligence Service, which deals with foreign intelligence and protects the UK from espionage activities outside the UK.

While royal visits to MI6 are usually announced in advance, William’s visit only became public knowledge after he left the premises.

Prince William, Duke of Cambridge, at the Earthshot Prize Awards Ceremony in Singapore, 2023
Prince William made a private visit to London’s MI6 headquarters on Thursday.Getty Images
The heir to the throne’s visit was published Friday morning in the Court Circular — the daily list of official royal engagements.

Still, details of the nature of his visit remain scarce, and it is not known with whom William had met.

Per the Telegraph, the Court Circular entry read, “The Prince of Wales this afternoon visited the Secret Intelligence Service.”

The father of three made a similar visit in 2022 when he was still the Duke of Cambridge.

And in 2012, William went to MI6 headquarters in London with his wife, Kate Middleton.

Prince William, Duke of Cambridge, attending the 'No Time to Die' World Premiere at Royal Albert Hall in London, England
The Prince of Wales, 41, made the hush-hush visit without his wife, Kate Middleton.WireImage

MI6 Headquarters, the SIS building, on the banks of the Thames in London, a large building with many windows
The British Secret Intelligence Service deals with foreign intelligence and protects the UK from espionage activities outside the UK.dpa/picture alliance via Getty Images
In 2019, William also spent a three-week stint working with the MI5, MI6 and GCHQ teams to gain a better understanding of how the UK’s security and intelligence agencies function.

“These agencies are full of people from everyday backgrounds doing the most extraordinary work to keep us safe,” the future king said at the time.

“They work in secret, often not even able to tell their family and friends about the work they do or the stresses they face.”

William’s visit came just hours after Buckingham Palace announced that King Charles had appointed the first-ever female chancellor of the Order of the Garter, Baroness Manningham-Buller, the former director general of MI5.

Prince William at the Army Aviation Centre in Stockbridge on May 13, 2024
While royal visits to MI6 are usually announced in advance, William’s visit on Thursday only became public knowledge after he left the premises.Getty Images
The visit also took place just two days before the king’s annual Trooping the Colour ceremony, known as one of the biggest events in the royal calendar.

While Charles has confirmed his attendance, it remains to be seen if the Princess of Wales, 42, will be making an appearance.

The princess has remained largely out of the public eye since announcing her cancer diagnosis in March, though recent reports suggest she’s “considering” making a balcony appearance over the weekend.