You know how it is - you've spotted a friend with his flies undone, so you sidle over, give him a nudge and say: "Mate - you're flying low". Same if they've got a large drop of gunk on the end of their nose: "Mate - wipe the snot off the end of your nose." It's all perfectly simple and perfectly straightforward: we say it like it is - "Hey - your skirt's tucked in your knickers!"
But things become much, much more tricksy when you're in a formal situation: when they've spent time and money on their outfit; when they're with bosses; when you're with people who are higher up the pecking order. In these situations, when you're not so sure of your ground, it can all become hideously embarrassing.
A while back, I was having afternoon tea, of all things, with some ladies and an elderly gent. I'm suited and booted and generally trying to behave myself such that I am even passing round the crustless cucumber sandwiches. The gent was wearing tweed suit and tie, and long red socks. In the manner of these grand old silverbacks, his knees were spread wide. I happened to glance down and nearly spat my tea out - he wasn't just flying low, his under-carriage was practically out on the chair. The ladies had already spotted this wardrobe malfunction; they didn't know where to look.
I leant over to the old gent - "Hey!" I hissed into his ear. "Your flies are undone!"
"What? What?"
"Your fly buttons are undone!"
"What was that?"
"You. Are. Flying. Low!"
"Ohh. Oh! Oh dear me!"
The undercarriage is retracted. The ladies shuffle awkwardly. I busy myself with another sandwich. Later, over a Tio Pepe sherry, the old buffer explained to me how, in starchier times, Brits had a ton of euphemisms for all these social faux-pas. I like them. I like them a lot.
Of course most of the time, it's fantastic that we can just say, "Oi mate - are you going to start breeding frogs in that sweat patch under your arm?" But there are still some sensitive folks who prefer more discreet ways of being alerted to their social gaffes.
For instance - seventy years ago, all you had to say was, "There's a star in the East", and every gent knew to check his fly-buttons. Similarly - "John's at the door," meant it was time to wipe the snot off the end of your nose.
And although some might like to believe that all these delicate euphemisms are pointless, and that today we can just say it how it is and call a spade a bloody spade, and yet... even now, pointing out these gaffes is a minefield.
I have a friend in the catering industry [Hi Nick!], who, most days, is an ultra-charming smoothie-chops Maitre D'. He's seen it all. He's seen everything. And every weekend, he is still confronted with a couple of social bloopers to which he has yet to find a solution.
First up: women with lipstick on their teeth. Come the weekend, Nick will be welcoming scores of beauties to the latest wedding of the year. He has yet to find a way of discreetly telling women that their front teeth are smeared with lippie.
Another Nick dilemma. Smartly dressed guys whose jacket collars are turned up. Men do not like being told that their collars are turned up - shows them up in front of their partners - and they hate, hate, hate having their collars smoothed down. Makes them feel like a schoolboy in short trousers.
It would be one hell of a sight easier for Nick and everyone else concerned if there were some tactful phrase that could give people the heads up without embarrassing them in front of their friends.
Other social howlers which are crying out - crying out! - for a diplomatic phrase to save your blushes?
They are legion!
* Women with skirt tucked into knickers...
* Guys whose shirt-buttons have popped to reveal great triangles of chest fur or belly flesh...
* Those unfortunates who have stepped in dog poo and are in the very act of treading it into the carpet...
* And those with faces smudged with oil...
* And food detritus caught in the teeth...
* And dentures that are on the move...
* And pee stains and worse, though perhaps it would be best not to go there...
And as for letting people know that they've got halitosis or rank bad B.O... It's risky! Very risky! A rare few have got the balls to tell a friend that they stink, but most people aren't up to it.
All we need - all we need - is just a dozen of those old-style Edwardian euphemisms and social harmony will be restored.
Here's a modest suggestion of my own to get you started - "There's a little birdie at the window"... which, with luck, will eventually come to mean: "Oi mate! Your wig is on the move!"