‘We’re moving out,” Megan tells me. Lily adds: “At the end of summer.”

I do not react to this momentous news with any great emotion. Call me sceptical, but as neither of them is in full-time employment, I’m not sure how this moving out plan is going to happen. I can tell from their enthusiastic descriptions of the place they envisage finding, and the area they’ll be looking in, that they’re not imagining the dumps I lived in when I left home: the one with hoary pipes zigzagging across the walls. Another where the bathroom had a permanently broken light, so you had to guess where your toothbrush was. Once, I nearly put superglue in my eye instead of eye drops.

I recount these anecdotes to prepare the girls for a reality check. But it’s as if a Victorian ghost has come to haunt them with tales of the slums. They wave me away with disbelieving sighs.

Lily and Megan’s idea of a first flat seems to be modelled on the Friends TV set: light, airy, comfortable, with kooky, amusing friends from next door popping by. Could my children be so unrealistic? If so, then I take some of the blame for overprotecting them, and for living in London. They’ve not had my desire to get away from the suburbs, so even in their mid-20s they have no experience of independent living.

“Just curious. How will you finance this move?” I ask them.

“A part-time job. To give me time to concentrate on my art,” Lily says.

“Don’t think part time will cover the rent.”

You have to prove you have a regular income or nobody will sign you up as a tenant

“We’re going to sell stuff on Etsy,” Megan, says with authority.

“But how will that make enough money? And it’s not consistent, is it? I mean, you have to prove you have a regular income or nobody will sign you up as a tenant.”

The girls roll their eyes in unison, (an eerie twin-thing).

“You don’t understand,” Megan says. “You have no idea how much people can make by selling things on Etsy or eBay. People didn’t do that in your day.”

“Yes, I had this old-fashioned thing called a career,” I tell them.

“It’s all about juggling and portfolio careers now,” Lily says.

“We’ll prove it to you,” Megan says. “We’ll customise jeans. People will pay good money for them.”

“Fine,” I nod. “Go ahead. Prove me wrong. I’d love you to.”

“Could I borrow £20? We need to source jeans in charity shops.” “And get some bleach.” Lily adds. “And dye.”

Upstairs, in the bathroom, the smell of bleach sears my nostrils. I blink watery eyes at my daughters, bent over the tub like medieval washer women, beating and stirring.

“There’s a small problem,” Lily tells me a few hours later. “Megan spilt a bit of dye.”

I go upstairs to find Megan crouched over a spreading green puddle on the new sisal carpet outside our bedroom. She’s scrubbing at it with a disintegrating J-cloth.

“Just warning you, after you move into your flat, I’ll be coming over to throw green dye on your carpet,” I tell her. “Then you’ll know how it feels.”

“That’s not very adult, Mum.”

The customised jeans are a success. They are dyed, bleached, embroidered works of art.

“How many did you sell?” I ask Lily.

She’s wearing a pair with one leg bleached white. Her sister’s are speckled all over like a green Jackson Pollock.

“A few. We can give you your £20 back.” “Soon,” Lily amends.

The bathtub is ringed with purple, like a fresh bruise. The stain outside my bedroom door is now a mud colour. But the girls are on a roll with their project, bringing armfuls of secondhand jeans back to the house, adding to the already overflowing piles of charity-shop clothes spilling out of their rooms.

Then I notice that the production process has ground to a halt.

“What’s going on with the business?”

Megan shakes her head. “It’s not ethical. We realised that the byproducts of bleach are poisonous. They take centuries to decompose.”

“What about all those jeans on the landing?”

“Oh,” she says airily. “We’ll drop them off at Oxfam.”

I can see that I’ll have to wait before I take my revenge with green dye. But on the upside, I do have a new pair of customised jeans.

Names have been changed

• Saskia Sarginson is the author of The Stranger (Piatkus, £7.99).