In fact, it makes you wonder why people buy shop made sandwiches at all. Look how cheap and easy it is to make your own. And it's the same with curries.

David E. Barton says instead of forking out for expensive takeaway meals you should learn how to make your own curries and stir-fries, for a fraction of the cost. So that's what I'm going to do this weekend, after I've been to a museum or maybe just walked along the river, enjoying the scenery.

As I walk along to the tube I feel pure and refreshed. Stern, almost. Look at all these people on the street, scurrying around, thinking about nothing but money. Money, money, money. It's an obsession. But once you relinquish money altogether, it ceases to have any relevance. Already, I feel I'm in a completely different mindset. Less materialistic, more philosophical. More spiritual. As David E. Barton says, we all fail to appreciate each day just how much we already possess.

Light, air, freedom, the companionship of friends… I mean, these are the things that matter, aren't they? Not clothes and shoes and fripperies.

It's almost frightening, the transformation that's already occurred within me. For example, I walk past the magazine kiosk at the tube station and idly glance over – but I don't feel the slightest desire to buy any of the magazines on offer. Magazines are irrelevant in my new life. (Plus I've already read most of them.)

So I get on the tube feeling serene and impervious, like a Buddhist monk. When I get off the tube at the other end, I walk straight past the discount shoe shop without even looking, and straight past Lucio's, too. No cappuccino today. No muffin. No spending at all – just straight to the office.

It's quite an easy time of the month for Successful Saving. We've only just put the latest issue of the magazine to bed, which basically means we can laze around for a few days doing nothing, before getting our act together for the next issue. Of course, we're meant to be starting on research for next month's article. In fact, I'm supposed to be making lots of phone calls to stockbrokers today, asking for their investment tips for the next six months.

But somehow the whole morning goes by and I haven't done anything, just changed the screensaver on my computer to three yellow fish and an octopus, and written out an expense claim form. To be honest, I can't really concentrate on proper work. I suppose I'm too exhilarated by my new pure self. I keep trying to work out how much I'll have saved by the end of the month and what I'll be able to afford in Jigsaw.

At lunchtime I take out my sandwich wrapped in foil – and for the first time that day, I feel a bit depressed. The bread's gone all soggy, and some pickle's leaked out onto the foil, and it really doesn't look very appetizing at all. What I crave at that moment is Pret Manger walnut bread and a chocolate brownie.

Don't think about it, I instruct myself firmly. Think how much money you're saving. So somehow I force myself to eat my soggy effort, and swig down some Ame. When I've finished, I throw away my foil, screw the top back on the Ame bottle and put it in our tiny office fridge. And that's about… five minutes of my lunch break gone.

So what am I supposed to do next? Where am I supposed to go?

I slump miserably at my desk. God, this frugality is hard going. I leaf dispiritedly through a few folders… then raise my head and stare out of the window, at all the busy Oxford Street shoppers clutching carrier bags. I want to get out there so desperately, I'm actually leaning forward in my chair, like a plant towards the light. I'm craving the bright lights and warm air; the racks of merchandise, even the bleep of the cash registers. But I can't go. This morning I told myself that I wouldn't go near the shops all day. I promised myself – and I can't break my own promise. Or at least, not so soon…

Then a brilliant thought occurs to me. I need to get a curry recipe for my home-made takeaway, don't I? David E. Barton says recipe books are a waste of money. He says you should use the recipes printed on the sides of food packets, or take books out of the library. But I've got an even better idea. I'll go into Smith's and copy out a curry recipe to make on Saturday night. That way, I can go into a shop – but I don't need to spend any money. Already I'm scrambling to my feet, reaching for my coat. Shops, here I come!

As I walk into Smith's I feel my whole body expand in relief. There's a thrill about walking into a shop – any shop – which you can't beat. It's partly the anticipation, partly the buzzy, welcoming atmosphere; partly just the lovely newness of everything. Shiny new magazines, shiny new pencils, shiny new protractors. Not that I've needed a protractor since I was eleven – but don't they look nice, all clean and unscratched in their packets? There's a new range of leopard-print stationery which I haven't seen before, and for a moment I'm almost tempted to linger. But instead I force myself to stride on past, down to the back of the shop where the books are stacked.

There's a whole array of Indian recipe books, and I pick up one at random, flicking over the pages and wondering what sort of recipe I should go for. I hadn't realized quite how complicated this Indian cookery is. Perhaps I should write down a couple, to be on the safe side.

I look around cautiously and take out my notebook and pen. I'm a bit wary, because I know Smith's don't like you copying down stuff out of their books. The reason I know this is because Suze once got asked to leave the Smith's in Victoria. She was copying out a page of the A-Z, because she'd forgotten hers – and they told her she had to either buy it or leave. (Which doesn't make any sense, because they let you read the magazines for flee, don't they?)

So anyway, when I'm sure no-one's looking, I start copying out the recipe for 'Tiger prawn biriani'. I'm halfway through the list of spices when a girl in WH Smith uniform comes round-the corner – so I quickly close the book and walk off a little, pretending I'm browsing. When I think I'm safe, I open it again – but before I can write anything down, an old woman in a blue coat says loudly,

'Is that any good, dear?'

'What?' I say.

'The book!' She gestures to the recipe book with her umbrella. 'I need a present for my daughter-in-law, and she comes from India. So I thought I'd get a nice Indian recipe book. Is that a good one, would you say?'

'I really don't know,' I say. 'I haven't read it yet.'

'Oh,' she says, and starts to wander off. I ought to keep my mouth shut and mind my own business – but I just can't resist it, I have to clear my throat and say, 'Doesn't she have lots of Indian recipes already?'

'Who, dear?' says the woman, turning round.

'Your daughter-in-law!' Already, I'm regretting this. 'If she's Indian, doesn't she already know how to cook Indian food?'

'Oh,' says the old woman. She seems completely flummoxed. 'Well, what should I get, then?'

Oh God.

'I don't know,' I say. 'Maybe a book on… on something else?'

'That's a good idea!' she says brightly, and comes towards me. 'You show me, dear.'

Why me?

'Sorry,' I say. 'I'm in a bit of a hurry today.'

Quickly I stride off, feeling a bit bad. I reach the CD and video section, which is always quite empty, and hide behind a rack of Teletubbies videos. I glance around and check no-one's about, then open the book again. OK, turn the page 214, Tiger prawn biriani… I start copying again, and I've just got to the end of the list of spices, when a stern voice says in my ear, 'Excuse me?'

I'm so startled, my pen jerks off my notebook and, to my horror, makes a blue line, straight across a photograph of perfectly cooked basmati rice. Quickly I shift my hand, almost covering up the mark, and turn round innocently. A man in a white shirt and a name badge is looking at me disapprovingly.

'This isn't a public library, you know,' he says. 'You think we run a free information service?'

'I'm just browsing,' I say hurriedly, and make to close the book. But the man's finger comes out of nowhere and lands on the page before I can get it shut.

Slowly he opens the book out again and we both stare at my blue biro line.

'Browsing is one thing,' says the man sternly. 'Defacing shop stock is another.'

'It was an accident!' I say. 'You startled me!'

'Hmm,' says the man, and gives me a hard stare. 'Were you actually intending to buy this book? Or any book?'

There's a pause – then, rather shamefacedly, I say, 'No.'

'I see,' says the man, tightening his lips. 'Well, I'm afraid this matter will have to go to the manageress. Obviously, we can't sell this book now, so it's our loss. If you could come with me and explain to her exactly what you were doing when the defacement occurred…'

Is he serious? Isn't he just going to tell me kindly that it doesn't matter and would I like a loyalty card? My heart starts to thud in panic. What am I going to do? Obviously, I can't buy the book, under my new frugal regime. But I don't want to go and see the manageress, either.

'Lynn?' the man's calling to an assistant at the pen counter. 'Could you page Glenys for me, please?'

He really is serious. He's looking all pleased with himself, as though he's caught a shoplifter. Can they prosecute you for making biro marks in books? Maybe it counts as vandalism. Oh God. I'll have a criminal record. I won't ever be able to go to America.

'Look, I'll buy it, OK?' I say breathlessly. 'I'll buy the bloody book.' I wrench it from the man's grasp and hurry off to the checkout before he can say anything else, my heart still thumping hard.