Maybe there is some sort of etiquette rule about what to do and what not to do when the high heel of a Duchess gets stuck in a drain?
And maybe it strictly forbids doing anything obvious like rushing to give assistance by kneeling down and gently levering the heel out of the narrow gap in which it is wedged. Maybe you're not allowed to touch any part of a Duchess, including the heel of her shoe.
Even so, that would only explain why the two members of the Irish Guards directly in front of the Duchess of Cambridge failed to come to her rescue when calamity struck at a St Patrick's ceremony at Aldershot. But what of her husband? William has been described rather generously as "gallant" when the embarrassing wardrobe malfunction occurred, but I can't see it.
After all, he only allowed his pregnant wife to hang on to his arm while she bent double in front of the Press and a barrack square full of soldiers to wrestle with the shoe and the grate on her own. And he grinned, as if to bond with the other men at the foolish ways of women. So not exactly stooping to conquer, either.
Of course, there won't be a woman who will look at those pictures and not wince in sympathy at Kate's mortification.
Men have always failed to understand high heels, except in the most obvious way.
Tell a man not to walk quickly because you are struggling to teeter along in your shoes and without fail he will take off like Usain Bolt.
Tell him you wouldn't mind sitting down soon because your feet are killing you and within 30 seconds he will have latched on to some desperate bore to stand and talk to for a good 20 minutes.
Tell him to give you a minute to change out of your flat shoes-for-driving into your spiky heeled boot before getting out of the car and immediately he will swing open the door, leaving you wrestling with your footwear in full view while he puffs around impatiently, muttering something about 'why you want to wear those things anyway'.
To which, clearly, the only answer is "so that I can put the dishes away on the top shelf when I've finished washing them, master".