Sarah Sands: Changing-room rage averted by shoppers' serenity

There are a few things from which celebrity cannot protect you. They include parking tickets and taking a restricted number of garments into shop changing rooms. Zara Phillips does not need to shoplift, but then neither do many shoplifters. Last week she was stopped from carrying too many Superdry items into a changing room. I don't quite understand why she needed to try anything on, since the only point is the name of the brand and, in the end, a T-shirt is just a T-shirt.

If you want to see what the complete breakdown of society looks like, visit a store's changing room at the end of the day. You could start with Bicester Village. Shop assistants are on all fours trying to make sense of the clothes mountains. I have worked, in the past, in the swimwear department of Harvey Nichols during the Christmas sales.

Perhaps the algorithms genius who has worked out how to speed up boarding on a plane could turn his mind to hustling clients through the changing rooms while working out if a bikini counts as one item or two, and later if it has been returned with its modesty strip in the vaginal area still intact.

The four or five items (on average) you are permitted to take in sound reasonable, but remember women are likely to want to try at least two sizes of each item. In the case of bikinis, they will then mix and match, say, a size 12 top with a size 14 bottom. All this has to be calculated in sauna-like conditions made more cloying by the clashing perfumes and antiperspirants.

There is the further issue of how many people you allow in with the clothes. Few women shop alone: there will be a mother or a best friend or, in the case of Bicester, a coach load of fellow Chinese students, wanting the sizes recalibrated in various time zones plus VAT exclusion forms.

It is like being a waitress with covers. There is a reason changing-room assistants knock on the door and call out "How is it?" knowing the customer is still fighting to pull the zip up past first base. All the profit is in the fast turnover. Also, once you have established personal contact, it is harder for a customer to wriggle away without buying anything. In New York, the assistants say their names slowly and clearly – "I'm SARAH" – so leaving empty handed becomes a personal betrayal.

The number system can exhaust shoppers into submission. If you are on your 10th item, it is tempting to buy it rather than return the last four ("How was it?") and join the queue all over again. I am surprised how little changing-room rage one witnesses, considering that the place resembles an airport departure lounge on a summer bank holiday – in fact, an airport departure lounge on a summer bank holiday where there has been a spontaneous walkout by baggage handlers and flights have been halted by a terrorist alert.

Last weekend, in New York, I watched a teenager and her friend try on two T-shirts and two pairs of mini-shorts. They then queued to buy one of the T- shirts and left victorious with their bag.

Ten minutes later, they returned the item, found to be damaged. Then back to the changing room to try on a replacement one. The process took just under an hour, but they were perfectly jaunty. I, meanwhile, was in a coma of boredom outside the changing room, waiting for my daughter. She would not be hurried. She understood Plato's wisdom that a good decision is based on knowledge and not numbers.