I am not good in clothes shops. I try on everything, I can't decide and at the till I generally find I'm holding something the wrong colour or the wrong style.

I then have to go back to the racks to find an alternative while the loaded-up shoppers behind me tut with impatience and start to buckle under the weight of security tags.

My inadequacies as a customer make me unpopular in shops at the best of times. During the sales season I'm surprised they don't ban me altogether.

I half expect to see posters of myself around stores bearing the words "Beware of this woman", or feel the grip of the floor manager's hand on my collar as I'm escorted off the premises for time-wasting.

Usually, I only go shopping when the shops are at their quietest (Tuesday mornings in February are good). But come January, I can't resist joining the throngs for bargains - and I almost always run into the same old difficulties.

It happened again this week. After much deliberation, I picked out a pair of M&S shoes that had been vastly reduced. Actually, I found the shoe for the right foot, which fitted nicely and decided the same would apply to the left. So I took a pair up to the till and prided myself on my efficiency.

However, when the assistant tried to scan the bar code, his machine wouldn't accept it.

"I can't think what's wrong," he said, trying again. I could already hear the rustle of restless sales shoppers behind me.

I inspected the shoes and soon spotted the problem (remember, I've done this before). "Ah," I said, beginning to redden. "I've picked up a six and a six-and-a-half by mistake. How silly of me. They should both be six-and-a-half. I'll just change one."

I took a shoe and barged my way through the shoppers back to the shelves where I'd found it. Unfortunately, I had picked up the six-and-a-half instead of the six, so I had to go back to the till to retrieve the other shoe and repeat my journey.

Thanks to all my fellow bargain hunters, the shelves were a mess - in fact, all at sixes and sevens, which is not helpful when you need a six-and-a-half. I had to hunt through the fours and fives before I found the one I needed.

By the time I had returned to the till, I was beginning to doubt whether or not I still liked the shoes. I'd just seen a nice pair of suede boots that I'd missed during my earlier trawl.

But I was far too embarrassed by then not to go through with the purchase. So I handed over my debit card and all those around me heaved a sigh of relief.

I had hoped I could sneak into our house with my shopping without my husband noticing. I wanted to inspect the shoes again before showing them to him as he has witnessed too many of my disastrous buys already.

But his ears are finely tuned to the crackle of plastic bags.

"New shoes, eh?" he said, emerging from the kitchen just as I was making a dash for the stairs. "Do they fit you? Ha, ha."

"I doubt it," I replied. "But they were a fantastic bargain."