I load the conveyor belt with a couple of cut-price bottles of Jacob's Creek, some ready-made pasta salads, a ready-made stir-fry, a couple of tins of dolphin-friendly tuna -- we're looking at a fairly dull middle-class lunch-break shop -- and then walk to the end of the checkout with my reused carrier bags, returning the cashier's automatic "hello" with a slightly distracted smile and a "hi", and wait for my shopping to start rolling towards me. The cashier picks up a bottle of wine, looks at the bottle, looks at me doubtfully, and then says "Could I see some ID please?"
I look back at her, momentarily confused. ID? For buying alcohol? I'm old enough that I don't expect it any more, but still about three years away from being flattered by it. But my brain catches up, and I say "oh, yes, hang on," and start ferreting around in my wallet.
As I'm fishing my driving licence out, and then as she's counting on a year at a time (I can see her lips moving) from 1978 to 2006, I suddenly realise what's going on. I'm wearing a knee-length grey skirt, grey woollen tights, a blue and grey stripy shirt, and black round-toed velcro-buckled sandals... Oh dear, oh dear.
I am in Tesco, at lunchtime, trying to buy wine, and I am wearing school uniform.