Prince Philip's remark to British students in China about them turning "slitty-eyed" always tops his list of gaffes, though the story behind it is far less well known.
The comment that kept coming back to haunt the Duke of Edinburgh characterised his off-colour quips and rankled with him ever afterwards.
It came on October 16, 1986 on the first and only British state visit to China, when the duke, the chancellor of Edinburgh University since 1953, met students from the institution who were starting a year learning Mandarin at Xian University.
"If you stay here much longer, you'll all be slitty-eyed," is the most common rendition, though other variants were reported.
Buckingham Palace confirmed comments to that effect.
But its reporting only came about thanks to a mix-up -- and, according to two biographies, the Chinese saying that puts his quip into context did not feature.
Chinese youngsters are told in jest by their elders not to stay too long in the West, lest they go "round-eyed": effectively, come home before losing their Chinese nature.
The prince's comment caused a furore in Britain -- though not in China.
The Sun headlined its front page "Philip gets it all Wong" while its tabloid rival the Daily Mirror went with "The Great Wally of China".
However, had things gone to plan in the royal press pack, the comment would never have surfaced at all.
'Absolute fluke'
The Sun's 1976-1990 royal reporter Harry Arnold said the chit-chat with students should have been observed from a distance from a pool position -- where one delegated journalist is posted to a pre-arranged position and shares the material with the rest of the pack.
"The reporter was missing from that position, so I sent back as pool captain to have these youngsters interviewed," Arnold told PBS.
"It was a fluke, absolute fluke, and it caught them floundering and of course my newspaper then had great fun by all these crazy headlines.
"It was just a terrible time for the duke and he suffered a lot of criticism as a result."
Alan Hamilton, the Edinburgh-born royal correspondent for The Times from 1982 to 2008, was the reporter responsible.
He wrote in The Times in 2011 that he recognised the students' accents and asked them about their encounter with their university's chancellor.
When he shared the students' account of the meeting with the "pool", the monarch's press secretary pleaded with the pack not to turn a joke into a diplomatic furore, but was unsuccessful.
The following day in Kunming, the prince was asked to comment on the uproar and said the students had been "tactless".
Student's apology
Simon Kirby, the 21-year-old student who revealed the conversation, was mortified by the uproar.
Contacted the following day by United Press International, Kirby said he "didn't mean to cause such a stir".
He said Prince Philip had asked him about his first six weeks in Xian.
"He said to me, 'By the time you go back home you'll have slitty eyes'," he told UPI.
"I told him that we don't live with Chinese students, to which he replied: 'So they (the Chinese) don't want to mix with the barbarians'."
Kirby also said the prince called Beijing "ghastly", and described the royal's remarks as "not very witty".
Thirty years later, documents released by the Foreign Office revealed that Kirby wrote to the British ambassador Richard Evans to make amends.
"I would like to convey my regrets to you for being the cause of such embarrassment to you and to the royal tour," he wrote.
"It was unfortunate for me that I was singled out and I have since suffered the consequences.
"Please be assured that I was in no way guided by anti-royal sentiments, I am certainly not some kind of Communist nutter."
Evans replied saying: "I now regard the incident as closed."
Taking offence
In a 2011 BBC television interview marking his 90th birthday, Prince Philip was combative when asked about it.
"Mr Hamilton. But for him, it wouldn't have come out. It had no effect in China, if that's what you're worried about," he said, tersely.
Hamilton himself defended Prince Philip's wisecracks as way to break the "high state of nervousness" that often accompany the "stiff formality" of royal visits.
"He (the duke) knows full well... that there is no better reliever of tension than a joke, preferably laddish, unexpected and slightly inappropriate," he wrote in 2011.
"It's rarely the people to whom the jokes are addressed who take offence; it's middle-class commentators, who view the duke as an embarrassing anachronism."