The arrest of the King's brother will catapult damaging shockwaves through the monarchy, which are already reverberating around the world.
I am writing this, sitting in GB News' Paddington studio, bringing you the latest details to our audience.
In all my years of royal reporting, I have never seen anything so historic and unprecedented.
Make no mistake, this is huge.
Even when we heard police cars had been spotted in Sandringham this morning, it didn't cross my mind that the activity would lead to an arrest.
I am still in shock.
Andrew Mountbatten-Windsor turns 66 today, but police most certainly didn't bring him a birthday cake.
The eyes of the world are now turning on Buckingham Palace, and not for a good reason.
In modern times, no senior royal has ended up in police custody, held on suspicion of such a serious crime.
Life imprisonment is the maximum sentence for someone found guilty of misconduct in public office, although the allegations are at this stage unproven and the police investigation must now run its course.
Mountbatten-Windsor has not been charged and has always denied allegations of wrongdoing.
For the last few weeks, there has been a slow drip feed of allegations emerging in the so-called Epstein Files. Emails released by the Department of Justice in the United States appeared to show the former prince shared reports of official visits to Hong Kong, Vietnam and Singapore.
Another file appeared to show he sent Epstein a confidential briefing on investment opportunities in Afghanistan.
Mountbatten-Windsor has always denied allegations of wrongdoing. I understand that the King and Buckingham Palace were not informed in advance that Mountbatten-Windsor was going to be arrested.
Perhaps a blessing in disguise, because it shows the Royal Family has not been given special treatment when it comes to the treatment of Mountbatten-Windsor.
The arrest of the King's brother will send damaging shockwaves through the monarchy. This is truly historic
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However, the King's brother, and Prince William's uncle, is still eighth in line to the throne. He still legally has, but no longer can use, his Duke of York title.
Only an Act of Parliament can remove these royal privileges. Not long after the news broke, King Charles released a seismic statement, saying he "learned with the deepest concern the news about Andrew-Mountbatten-Windsor and suspicion of misconduct in public office".
The personal family relationship between siblings was scratched from the record. The Crown, taking priority over the Mountbatten-Windsor family.
I understand the Prince and Princess of Wales support the King's statement. This is now a damage control exercise; the Royal Household will be fighting to save the reputation of the monarchy.
King Charles wanted to remind the public of their purpose, ending his statement with: "My family and I will continue in our duty and service to you all.
"Duty and service" is the lifeblood of the institution, and there are not expected to be any changes to the Royal Family's official programme of engagements.
They want to exist to serve the wider public good, but new polling by Ipsos shows a slump in their popularity. The shadow of Thames Valley Police's investigation, and potential investigations by other police forces, will hang over the Royal Family for some time to come.
Republicans, unsurprisingly, have called for the King and the Prince of Wales to publicly [sic] disclose what they knew and when. The King has already said "the law must take its course".
However, Pandora's box may well have been opened, as questions continue to be raised over Mountbatten-Windsor's actions and the actions of those close to him.