Personally, I blame the rain. It was hammering down as friend Diane and I walked to the pasta and wine place.
The weather meant I'd taken off my glasses and chucked them in my handbag, and we were marching at top speed. Typically, both of us had managed to leave all of the millions of umbrellas we own at home.
Otherwise I'd have spotted the note stuck, no pinned, to the back of Diane's coat. It was only as she sped ahead to push open the restaurant door that I realised something was amiss and hurried to catch up with her, so we almost fell into the place together.
The result was that the friendly waiter who tried to take her coat narrowly avoided a scuffle with me as I grabbed Diane by the collar and began tugging the damned thing off as she screeched: "What on earth are you doing?"
Perhaps he thought we were a lesbian couple having a bit of a domestic, who knows? In any case, he obviously knew better than to tangle with apparently mad middle-aged women and scuttled backwards in a manner which would impress Manuel of Fawlty Towers.
"You have COW on your back. Well, Cheap Old Woman actually, but, look, the little letters have run a bit in the rain and now all it mostly says is COW," I explained as we snapped off the special message.
Of course we instantly knew who had done this. Diane's lovely daughter, Tamsin.
Just two hours earlier Diane had yelled at Tamsin: "Do I look like I've got IDIOT written on my forehead. Can you see a SOFT TOUCH sign on me anywhere? No, so pack it in."
All this started because Tamsin wants to move into a shared flat with three friends, all around 16 or 17.
They have part-time jobs plus college and if their parents would just see sense, and pay a bit towards the rent, and stump up a deposit, and not let the landlord know that really a gang of teenagers are moving in, well, everything would be lovely.
When you are 16 it's that simple. Just get a flat and you can have all your mates round, come in when you like and drink weird cocktails. You'll never again annoy your darling parents by going clubbing in half a dress, the fact that there's no hot water left, or dodgy looking boys are hanging around.
Diane's answer to the magnificent flat plan was, perhaps, a mistake. She told Tamsin: "Ha, ha, ha, ha. I'd rather pay you to stay here. Honestly, that's the truth."
So Tamsin now thinks her mother should stump up cash for the privilege of cruelly holding her own daughter hostage at the family home. With the purse firmly shut, she's taken to advertising her outrage.