Christine doesn't mean to do it. She is just passing and notices it in the hi-fi shop on the way to the supermarket. She has pound;40 to spend on food, and that is it until pay day. Still, she can always live on baked beans and potatoes for the rest of the week. An easy decision, really. She makes the down-payment on the CD mini-system on special offer and walks home with it.
This senior teacher in a large primary in the North-East knows she over-shops. She already has pound;25,000 in bank loans, not counting the pound;4,000 she owes on her 24 credit and store cards - a debt larger than her fiance's mortgage. She thinks she may have to get counselling for her spending and admits to carrying a card for a teachers' helpline. It's just that she hasn't got around to calling them yet.
Her colleagues at school think it's a joke - her 25 full-length, evening dresses at pound;100 a throw, her weakness for buying two of everything - but they don't know the true scale of her spending sprees.
At 30, she earns around pound;23,000. She's been picked out as a high-flyer and is well on her way towards her national professional qualification for headship. But the greater the pressure, the more she spends.
Christine (not her real name) blames her perfectionism and the relentless nature of teaching for her shopping excursions. Despite putting in long hours, she feels that failure is always just around the corner.
"Either you get the children through (in the tests) or it's your fault. If I don't get them through I'm going to let them down, let the school down and let the parents down - I am the unworthy one. So I think, 'No one cares about me so I'll look after myself, I'll feel good about myself and I'll look good'. That works for a while, but then it stops."
Last November, buoyed by a pound;2,000 pay rise, she took to the high street in search of a perfume to suit her new senior-teacher image. She came back with a bottle of Hugo Boss and an pound;800 designer leather coat which she hid - sales tags still on - and dared not wear for more than four months.
Despite regular purges of last season's fashions, often worn only once or twice before being sent on to Oxfam, Christine now has three walk-in double wardrobes crammed with clothes. She has 60 pairs of shoes, including ankle boots, strappy shoes, open-toed sandals and stilettos, plus her pound;90 trainers. She has seven business suits, having bought two just recently (cost: pound;270) in preparation for deputy headship interviews (although in the end she decided she would be more comfortable in one of her old favourites).
Christine's is a costly addiction. She spends two-thirds of her monthly salary on either shopping (usually about pound;300 a month) or debt repayment (pound;450 a month). This leaves about pound;400 to cover food and other necessities. She plans to get married next year but, according to her loan and repayment spreadsheets, cannot afford to have children for at least five years.
"I'm due to clear my debt in about seven years. At the moment I think I can manage it; I've worked out the facts and figures. I've cut down a lot from what I was like. I feel I've peaked and I'm getting sensible."
Dr Robert East, of Kingston university's business school, estimates the number of people in Britain whose shopping habits are out of control at a few per cent of the buying population - on a par with the US, where 15 million show symptoms of a "deviant pattern of compulsive purchasing".
He says the problem is more common among women and can cause a "huge amount of distress" for them and their families. No particular profession or social demographic group appears to be especially vulnerable, but research suggests that people with both a high materialistic streak and a low ego are most susceptible.
Martin Lloyd-Elliott, a counselling psychologist in London, draws a clear distinction between true shopping addicts whose consumer behaviour is out of control - a very low percentage - and the large number who have problems managing their money and may have addictive behaviour.
He says part of the difficulty in dealing with the addiction lies in the fact that the term "retail therapy" is used in a light-hearted way, mocking today's consumer-driven society.
"People who are genuinely out of control around their money and shopping deserve some respect and sensitivity. They are not just stupid or lazy; they are suffering from a behaviour problem. I've known some who have bought thousands of pounds worth of things, taken them home and never unwrapped them."
He compares addicts' experience of shopping with the euphoria felt by compulsive gamblers. "That feeling is quickly followed by depression, anxiety, remorse, guilt and self-hate."
Christine shops because she thinks she deserves a bit of pampering; she works from 7am to 11pm most days and she feels calmer after a big splurge. She lost five stone two years ago, and the joys of spending became so much sweeter with a size 10 frame. (It was not simply a case of transferring her compulsive behaviour from food to shopping; she went to Weight Watchers for two years because she felt her weight was preventing her from being an effective teacher.) She likes to buy two of each item - or three if it's lingerie - and sometimes buys two identical garments to disguise what she's done ("after being like this for a while I've got sneaky"). She often comes home with a gift for her partner "to alleviate the guilt".
For her wedding next year she has promised herself she will not start even looking for a dress until three months before the big day. She knows that otherwise she'll buy two.
She also knows she's not alone with her problem. Once a month she goes on a shopping expedition with a fellow teacher who, although younger and on a lower salary, is already nearly pound;8,000 in debt.
Christine was upset when her fiance called her a coward because she couldn't bring herself to cut up even one of her credit cards - something she can't really explain. "I think I just like looking at them. I think if I put them all together I'd have pound;40,000 in money that's not really money. I think, 'That's how much my life is worth'. People want to give me money. And if someone is giving you something for nothing, it means they trust you.
"If you are in control of your finances you are in control of your life. I've got control over all this money, although sometimes it feels like it's ruling me. But I can juggle my payments. I can rob Peter to pay Paul."
She has loans of pound;10,000 and pound;15,000 with two separate banks. The debts began to accumulate about six years ago, soon after she started teaching, and at one point she was forced to move into cheaper accommodation because she couldn't afford to shop and pay the rent. "I'd rather shop than eat," she says. She has never regretted her decision to become a teacher - "I can't see myself doing anything else" - but admits she is never happy with her own work. "I'm always mentally measuring myself against all the standards in the world and feeling like I'm not making it.
"The best word is probably frustration. Just when I think I'm on top of it, it suddenly feels like I'm not even treading water. It feels like I'm being pulled down."
And her worst shopping moment? A green dress she bought for pound;60 which didn't quite fit so she paid another pound;60 to have it altered. But in the meantime she lost weight and it looked terrible on her. "I felt really angry with myself; I already had about five green dresses."
Corinne Usher, a consultant clinical psychologist at Amersham general hospital in Buckinghamshire, says retail therapy is fast becoming a curse rather than a cure - and not just for women. "Money is valued and spending it lavishly might make people feel valued," she says. "A lot of people shop because they are very, very anxious. It's a great distraction, it takes time and effort and there's a fantasy element about it."
Over the past 10 years, compulsive shopping has started replacing compulsive eating as a major problem for her clients who, she says, generally arrive with a "constellation" of symptoms which mask other problems. "You have to help compulsive shoppers try to understand what dilemma they are dealing with and help them find solutions that are more appropriate - and cheaper."