"Retail guru" Mary Portas details the ten worst customer service crimes. I can see where she's coming from on the first nine points, but on point ten she commits one of the most annoying and baffling acts a customer can do in a shop.

"I popped into Superdrug to get some hair ties for my daughter but the rack was empty. So I went up to this assistant to ask, and sure enough, she went, "If it's not out on the floor, we haven't got it." I think they’re lying and just can’t be bothered to look."

Aaaaaaaaargh! The instant you ask the question "do you have any more of the thing that isn't on the shelf?" you're doing it wrong. What you're effectively asking is, "Hello, I see the shelf has run out of hair ties, but do you have any more? Perhaps behind the counter there's a gateway to another dimension in which resides a magic stockroom of infinite everything? Failing that, maybe you're trying a radical new retail technique whereby instead of putting stock out on the shelf, where it can be sold and from which you can turn a profit, you've hidden it somewhere out of the customer's view to keep sales down?"

Perhaps, in some fleeting moment of hideously misplaced optimism, she expects the sales assistant to reply "Aha! Well done! We hid all our stock to discourage people from buying it, but now you've asked for it you've passed our little test!" before turning a key underneath the counter to activate a hitherto unnoticed glittering podium that slowly rises up through the floor in a cloud of dry ice and flashing lights, upon which is a velvet cushion with a single hair tie on it. "Congratulations, you've won tonight's star prize!" says the store manager over a backdrop of game-show music.

That in itself is bad enough. But worse, even worse, is that when the assistant, contrary to the customer's expectations, doesn't do any of the above, but instead patiently explains, "look, if we had any of it, it would be on the shelf, that being where we keep the things that are for sale", the customer complains and writes a whiny article in the paper like it's the shop staff who are in the wrong.

I'll make it very clear, and hopefully customers like this will read this article and help make shopping a marginally less unpleasant experience for everyone.

If you want to buy a particular item, and you can't see that item anywhere in the shop, that means they're not selling it. This could be for two reasons; either they don't sell it, or they normally do sell it but they've run out. You can normally tell which by the presence or absence of an empty shelf with the name of the thing you're looking for on it.

As ever, there are a few exceptions which really ought to be obvious and go without saying. One is Argos. Yes, all their stock is hidden, but they get around the problem by publishing a clearly categorised and indexed catalogue of all the things they sell, and putting little keypads in the stores so you can check yourself if they've got any without having to queue and ask someone. Even so, one wonders if there are still die-hards who ask the sales staff things like "I know engine oil isn't in your catalogue, but do you sell any?" or "your electronic stock system says you've run out of Nintendo Wiis, but can you have a look?" then get annoyed when they're referred back to the catalogue or stock system that's there for the purpose.

The second exception is if you're looking for one of a very limited set of products that can't legally be put on the shelf for you to take, such as fireworks or cigarettes. If so, then fine, ask away. But things like bread, milk and hair ties aren't going to magically appear just because you spoke to someone. And if for some reason they really are indulging in the idiotic pastime of hiding the stock somewhere until you ask for it, then just go to another, less moronic, shop. Their loss.