In June, the Duke of Edinburgh will turn 100. Photo / Getty Images
He once said he "couldn't imagine anything worse" than living to 100.
But as the Duke of Edinburgh fast approaches the milestone, Buckingham Palace aides, well aware that it will be a moment of national celebration, find themselves in rather a quandary.
"Let's just say we have a rather reluctant celebrant," one told the Telegraph.
"You can't do something if someone doesn't want something doing."
Planning for the big day, June 10, will begin in earnest in the New Year.
But the Duke, who endured almost seven decades in the spotlight, has relished his retirement and has no desire to re-emerge from the shadows, particularly for something as frivolous as a birthday.
One tradition that he cannot avoid however, and which is certain to raise a smile over the royal breakfast table, is the congratulatory telegram from the Queen, which he will receive just like any other British citizen turning 100.
Never one to want a fuss, the Duke has spent most of the last three years in blissful solitude.
Until recently, he had lived at Wood Farm on the Sandringham estate, whiling away his days reading, writing and painting.
However, in mid-March, with the onset of the pandemic, he relocated to join the Queen at Windsor Castle, where they tend lunch or dine together most days, spending more time together than they have done in many years.
The Duke was last seen in public in July, when he formally handed over his role as Colonel-in-Chief of The Rifles in a low-key ceremony at Windsor.
Prior to that, he was photographed leaving the King Edward VII Hospital in London on Christmas Eve 2019, following treatment for a "pre-existing condition",
The odd portrait has otherwise been published, most recently to mark the Duke and the Queen's 73rd wedding anniversary.
When he turned 99, the Duke was said to be "characteristically taciturn" about the occasion, opting to mark it with a quiet lunch.
He did, however, agree to be pictured with his wife "just in case" and the palace duly released a rare new photograph of them standing side by side in the quadrangle at Windsor Castle.
Next year will be a different matter and his reluctance for a public celebration is likely to be overruled.
Although the pandemic renders future events uncertain, aides are keenly aware that the occasion will have to be appropriately marked, even if plans have to be stripped back.
"It is something that will have to be raised in the New Year," one said.
"But we might get short shrift.
"The one person you can guarantee will not want anything to do with it, is the Duke. He's retired, he's stepped back, he doesn't want the fuss. You can't blame him."
If coronavirus restrictions allow, the royal family will certainly gather for a private celebration, and the Duke and Duchess of Sussex are hoping to fly over from California to attend.
The date coincides with the Duke's Invictus Games, due to begin in The Hague on May 29.
The Duke will become the first male member of the royal family to turn 100 and the first royal consort to do so.
At 80, when discussing the Queen Mother's 100th birthday, he told the Telegraph he had "no desire whatsoever" to reach the same age.
"I can't imagine anything worse," he said. "Bits of me are falling off already."
When the Queen Mother reached the milestone in August 2000, there was a procession down The Mall and a Buckingham Palace balcony appearance.
One event said to be in the pipeline for the Duke is a photography exhibition to be curated by the Royal Collection Trust during its annual summer opening of Buckingham Palace.
However, the organisation has not yet confirmed plans for the event.