Alarums! Royal protocol has been breached once more, and the chatterati is all in a tizz. The latest atrocity was committed by Julia Gillard, the Australian Prime Minister, when she failed to curtsy to the Queen. She wasn't even wearing a hat! But we'll leave that to one side for now.
What's got the courtiers spluttering is that Ms Gillard shook hands with the Queen on Wednesday, when everyone knows that a) you never touch the monarch, and b) a woman is supposed to look down, dip her head and bob her knees. For men, it's a bow, though only from the shoulders, not from the waist.
Or is it the other way round? And that is the problem with etiquette – nobody can quite remember what to do. In the starched tension of the moment, knowledge of arcane court ritual has a habit of evaporating. This is why Buckingham Palace's advice is simple: "Do whatever feels comfortable." And in Ms Gillard's defence, this is what she was doing.
The trouble with curtsying is that few people could ever say it "feels comfortable". Zara Phillips, the Queen's granddaughter, who wears jeans and drives a Range Rover Sport, says she can do it only because she grew up with it, but that not many people know how to do it.
This is because curtsying has always been a contrivance, which is anyway sort of the point. The word is a shortening of courtesy. As an act of deference, it stems from the 17th century, when the curtsy and the bow were more or less the same – an extravagant gesture like those performed in Restoration comedies, one leg behind the other and a big sweep of the arm. Only when ladies' skirts got bigger did it become a more elaborate operation. Maintaining your balance while slightly lifting your skirt and bending your knees is – I can only imagine – not easy.
To confirm this, I speak to the etiquette expert Mrs Harbord – she of the reality TV series Ladette to Lady. Curtsying, she says, is not instinctive: it has always been something you learn. "The first rule is practice. When I worked at finishing school many years ago, at Winkfield Place, curtsying was still a regular occurrence. It's just not something we do any more. But it was always something you had to practise at home."
The second rule, she says, is never to wear a tight skirt. Sarah Brown overcame that obstacle by performing an exemplary curtsy to the Duchess of Cornwall in 2007 despite wearing a power suit. No doubt she was mindful not to be associated with Cherie Blair, who committed the least forgivable gaffe 10 years previously, by failing to curtsy to the Queen on arriving at Balmoral. On Her Majesty's home turf, that was just plain rude.
Mary Killen, etiquette expert for The Spectator, says curtsying has another purpose. "It can be helpful to people in a social occasion if people starting dropping to their knees like a pack of cards, because it signals that there is a royal present. It also clears the way so that those at a distance get a chance for a good gawp."
She believes there has been a renaissance in interest in good manners, and is hoping to open a finishing school in the offices of The Lady magazine in central London, at which curtsying would be taught.
Defenders of Ms Gillard say that she was just being consistent. As a republican who has called for ties with the monarchy to be severed once the Queen's reign ends, she had a duty not to defer. To be elected as a republican, only to start bowing and scraping on meeting the Queen, might have smacked of hypocrisy.
The trouble with ignoring protocol is one of perception. If what you feel most comfortable with is flaunting the rules, that can say a lot about you. It can say you are arrogant and disrespectful. And not wearing a hat was clearly no accident.