What if I’m on the Atkins diet?

I look around furiously, but Jess is nowhere to be seen. And the bloody thing’s too heavy to lift on my own. Where’s she gotten to, anyway?

Suddenly I spot her coming out of a side door, holding a big cardboard box and talking to a store employee. What’s she doing now?

“I’ve been speaking with the produce manager,” she says, approaching me. “We can have all these bruised bananas for nothing.”

I look in the box and it’s full of the most revolting, manky bananas I’ve ever seen.

“They’re perfectly good. If you cut away the black bits,” says Jess.

“But I don’t want to cut away the black bits!” My voice is shriller than I intended, but I can’t help myself. “I want to have nice yellow bananas! And I don’t want this stupid great sack of potatoes, either!”

“You can make three weeks’ worth of meals from that one sack,” says Jess, looking offended. “They’re the most economical, nutritious food you can buy. One potato alone—”

Please! Not another potato lecture.

“Where am I supposed to put them?” I interrupt. “I haven’t got a cupboard big enough.”

“There’s a cupboard in the hall,” says Jess. “You could use that. If you joined a warehouse club you could use it to store flour and oats, too.”

Oats? What do I want oats for? And anyway, clearly she hasn’t looked inside that cupboard.

“That’s my handbag cupboard,” I point out. “And it’s totally full.” Jess shrugs.

“You could get rid of some of your handbags.”

Is she seriously suggesting I should get rid of some of my handbags… for potatoes?

“Let’s carry on,” I say at last, and push the trolley forward as calmly as I can.

Stay polite. Stay gracious. She’ll be gone in twenty-four hours.

But as we progress round the store I am really starting to lose my cool. Jess’s voice is constantly droning in my ear like a bumblebee, on and on until I want to turn round and swat her.

You could make your own pizzas for half the price… Have you considered buying a secondhand slow-cooker?… Store-brand washing powder is 40p cheaper… You can use vinegar instead of fabric softener…

“I don’t want to use vinegar!” I almost snap. “I want to use fabric softener, OK?” I put a bottle of it into the trolley and stalk off toward the juice section, Jess following behind.

“Any comments?” I say as I load two cartons into the trolley. “Anything wrong with lovely, healthy orange juice?”

“No,” says Jess, shrugging. “Except you could get the same health benefits from a glass of tap water and a cheap bottle of vitamin C tablets.”

OK. Now I seriously want to slap her.

Defiantly I dump another two cartons in my trolley, yank it round, and make for the bread section. There’s a delicious smell of baking in the air, and as I get near I see a woman at a counter, demonstrating something to a small crowd of people. She’s got a shiny chrome gadget plugged into the wall, and as she opens it up, it’s full of heart-shaped waffles, all golden brown and yummy-looking.

“The waffle-maker is quick and easy to use!” she’s saying. “Wake up every morning to the smell of fresh waffles baking.”

God, wouldn’t that be great? I have a sudden vision of me and Luke in bed, eating heart-shaped waffles and maple syrup, with big frothy cappuccinos.

“The waffle-maker normally costs £49.99,” the woman is saying. “But today we are selling it at a special reduced price of… £25. That’s 50 percent off.”

Fifty percent off? OK, I have to have one.

“Yes, please!” I say, and push my trolley forward.

“What are you doing?” says Jess.

“I’m buying a waffle-maker, obviously.” I roll my eyes. “Can you get out of my way?”

“No!” says Jess, planting herself firmly in front of the trolley. “I’m not going to let you waste twenty-five pounds on a gadget you don’t need.”

I’m outraged. How does she know what I do or don’t need?

“I do need a waffle-maker!” I retort. “It’s on my list of things I need. In fact, Luke said only the other day, ‘What this house really needs is a waffle-maker.’ ”

Which, OK, is a bit of a stretch. What he really said was “Is there anything for breakfast except Coco Pops?”

But he might have done. How would she know he didn’t?

“Plus I’m saving money, in case you hadn’t noticed.” I push the trolley round her. “It’s a bargain!”