What if you go to the assistant and say: 'Those kids are nicking T-shirts' and the assisant turns out to be a gum-chewing dimbo who can only say: 'So?' Or to be too busy filching stock from behind the till to give a damn? What if the assistant leaps out and arrests the wrong-doers and wants your name and address and in two years' time you have to go to court and give evidence while the family of the accused spit and hold up signs saying 'We Know Where You Live'?
What if the felon turns out to be the shopkeeper's son, just picking up some eggs for the family tea? What's it to do with you anyway?
I once saw a woman with dirty hair and three children co-ordinating the lifting of pints of milk in a supermarket. I left them to it.
When I was a youngster I knew a remarkably talented group of shoplifters: the thing was to filter silently through Biba (when it was a department store on High Street Kensington), stealing everything in sight, floor by floor up as far as the Rainbow Room.
They would then compare booty in the fifth-floor Ladies', and then put it all back again on the way down.
If you really wanted something you would keep it and tell your mother you had got it at the Oxfam shop, but the kick was the skill, not the acquisition. Not being good enough to put things back was as looked down on as not being good enough to lift them in the first place.
Shoplifters nowadays have no class. They don't care who sees. They know that you are not going to say anything, because this is London and who gives a damn what anybody else does? They smirk, they wink, and they make you complicit.
A shaven-headed youth did this to me the other day in a food shop on the Uxbridge Road. He was pinching chewing gum from the rack by the till, while the assistant was getting cigarettes down for his friend.
I saw him, he saw me see him, he smirked. I found myself saying: 'Can't a big boy like you afford to pay for his sweeties then?' Oh my God, that's it, I thought, he's a computer-age, video-nasty psycho youth and he's going to kill me.
I could imagine the headlines: 'Dead for a packet of chewing gum; have-a-go mum knifed in Shepherds Bush.' But no. He said: 'Naah, it's all right.'
Success flooding to my head, I said pompously: 'It may be all right for you.'
'Naah,' he said once more, and his grin changed. 'I'm going to pay for it. And he did.
He hadn't been going to, but he did. So did I save my local store from the final chewing-gum theft that would have bankrupted it? Or am I just an idiotic and suspicious busybody?
All I know is I hate that assumption that no one gives a damn.