It took just six words spoken on national television for the Prince of Wales to decide enough was enough.
His younger brother, Prince Andrew was being raked over the coals for his disastrous interview on BBC Newsnight, last Saturday, where he struggled to explain his long-time friendship with convicted sex offender Jeffery Epstein.
But on Tuesday night, as families across Britain sat down to watch the first election debate between Conservative Prime Minister Boris Johnson and Labour leader Jeremy Corbyn on ITV, it appeared much more than the "party prince's" reputation could be at stake.
After probing the Conservative and Labour Party leaders on hot-button election issues such as Brexit and the National Health Service (NHS), journalist Julie Etchingham delivered a quickfire round.
"Is the monarchy fit for purpose?" she asked.
It must have been a truly heart-stopping moment for the royal family, whose survival rests on keeping well out of the political arena.
After years of soaring popularity – thanks to a string of high-profile royal marriages and births – it had become a campaign issue.
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But the worst was still to come.
"Needs a bit of improvement," Corbyn said, sparking wry laughter from the audience.
Johnson, however, was a little more careful.
"The institution of the monarchy is beyond reproach," he said.
Etchingham then followed up with another question, which ultimately sealed Prince Andrew's fate.
"Is Prince Andrew fit for purpose?" she asked.
The audience was silent now.
"Before we discuss Prince Andrew, I think we should discuss the victims that are there because of what Epstein was doing," Corbyn replied.
"I think there are very, very serious questions that must be answered and nobody should be above the law. But the primary position ought to be the proper treatment of those people, the victims of the most appalling behaviour by apparently Epstein and many others."
Johnson said: "All our sympathies should be with the victims of Jeffrey Epstein and the law must certainly take its course".
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For the royal family to weather an embarrassing scandal is one thing – they have suffered many before. However for that scandal to cloud a democratic debate and become an election issue was seen as beyond the pale.
A royal source told The Times those questions were the very last straw.
"Prince Charles and his private secretary were determined that this should not be allowed to drag on and on. The question of the election was critical," they said.
The view chimed with those of senior aides who had expressed their fears to the Queen. Prince Charles is said to have urged the Queen to strip Prince Andrew of his duties. The monarch, 93, acted swiftly in summoning Prince Andrew to a meeting that saw him step down for the "foreseeable future".
Prince Andrew himself had described the scandal as a "constant sore" for his family.
"After her error of judgment when she let Andrew do the interview, the palace are keen to show a decisive Queen," former BBC correspondent Peter Hunt said on Twitter.
"But it's Charles and his people who are increasingly pulling the strings."
At 6:00pm (local time) on Wednesday, Buckingham Palace released a statement announcing Prince Andrew would step down.
"It has become clear to me over the last few days that the circumstances relating to my former association with Jeffrey Epstein has become a major disruption to my family's work and the valuable work going on in the many organisations and charities that I am proud to support," the Duke of York said.
"Therefore I have asked Her Majesty if I may step back from public duties for the foreseeable future, and she has given her permission."
It was over.
Now the royal family is bracing for a subpoena, which will ask the Duke to give evidence about his ties to Epstein under oath.
In the meantime, their focus will no doubt be on damage control.
On Friday, the Queen was seeing taking Prince Andrew horse riding on her Windsor estate in a show of personal support.
A royal source said: "The Queen was privately very disappointed with Prince Andrew, despite the public efforts to rally round.
"It's wrong to think that she just accepted his version of events, that the interview had gone well and there was nothing to worry about.
"She saw the fallout and was very unhappy. She has spent her whole life protecting the monarchy and in just one week her son's actions threatened to tear it apart.
The latest government stats show just 19 per cent of British people have a positive opinion of Prince Andrew, and just six per cent believe he's telling the truth about Epstein.
A whopping 47 per cent believe the saga has damaged the monarchy, but it remains to be seen if it's beyond repair.