Prince Harry and his wife Meghan's unilateral decision to walk away from front-line royal duties leaves the British monarchy's future wobbling.
It also piles the pressure on his brother Prince William, who, along with his wife Kate, will have to shoulder more of the burden of representing the institution to a younger generation.
Harry, 35, and Meghan, 38, the Duke and Duchess of Sussex, were set to become an increasingly important cornerstone of the monarchy in the decades to come.
But their shock decision to step back from being senior royals throws all that up in the air.
Queen Elizabeth II is 93 and it has long been signalled that when her eldest son Prince Charles inherits the throne, he wants a slimmed-down monarchy tightly focused on him, his wife Camilla, his sons William and Harry and their children.
Harry's role was meant to be as a rock of support to William as he in turn becomes heir to the throne, prince of Wales and eventually king.
The two brothers were exceptionally close growing up, together coming through the death of their mother Diana, princess of Wales, in a 1997 car crash when William was 15 and Harry 12.
But Harry's determination to go his own way with Meghan has seen the brothers -- at Harry's own admission -- drift apart.
While William is a cautious character, Harry is combustible and prone to impulse.
Harry's announcement that he and Meghan will step back, rip up relations with the media, partially relocate to North America and seek a private income -- without having consulted Queen Elizabeth or Charles first -- will have done little to diminish his hothead reputation.
And the monarchy has traditionally been ruthless in cutting loose rogue royals to ensure the institution's survival.
King Edward VIII chose to abdicate in 1936 in order to marry twice-divorced US socialite Wallis Simpson. They lived the rest of their lives in exile in France.
In 1996, Diana was stripped of the title "her royal highness" when she divorced Charles, as was Sarah when she divorced Prince Andrew, Queen Elizabeth's second son.
Andrew himself was forced to cut all royal duties for the for the foreseeable future in November last year, following a bungled television interview on his relationship with convicted US sex offender Jeffrey Epstein.
During Queen Elizabeth's long reign, she ran affairs of state while her husband Prince Philip, the royal patriarch, ran the family.
But he retired in 2017 and at 98 now spends most of his time at Sandringham, the sovereign's private estate in eastern England.
A naval officer, he liked to run a tight ship and the Windsors might be missing his pragmatic, no-nonsense approach to ironing out the family's problems.
A successful television actress and activist, Meghan was initially seen as a breath of fresh air for the royal family when her engagement to Harry was announced in November 2017.
Mixed race and with a career of her own behind her, she was seen as someone who could modernise the monarchy and represent it to a new generation in multi-cultural 21st-century Britain.
It was assumed that unlike Diana, who was 19 when she got engaged to Charles, Meghan -- who married Harry aged 36 in May 2018 -- was old enough and wise enough to know what she was letting herself in for.
However, the gilded straightjacket of life within the British royal family -- governed by centuries of precedent -- seem to have left the Los Angeles former TV star cold.
"I never thought this would be easy but I thought it would be fair," she told ITV television in October, admitting that life as a new mother had been hard.
Talking of "complicated issues", Buckingham Palace's rushed brief statement on their shock announcement hinted at sympathy for their position.
But it remains to be seen whether the Sussexes' attempt to be half-in, half-out of the royal family will last long.
The track record of royals trying to earn money outside the family firm is not good.
Harry and Meghan might eventually find their pre-destined life inside the royal circle much easier than going it alone.