They puke under the bed, crap in the house plants and leave dead frogs in my slippers. These are not toddlers, but a pair of creatures who sleep in my bed all day, keep me awake all night, have chronic halitosis, and eat only mackerel in aspic: Devon and Tess, both four years old, are felines.

I can't recall life before cats. It was certainly cheaper - by about pounds 680 a year - and that excludes initial set-up costs: cat transporters, litter trays, pooper-scoopers, baskets, fleecy igloos, electromagnetic cat flaps, collars, name discs, feeding bowls, electronic timed feeders, jabs and castration. Let's call that lot pounds 400.

Other costs are unquantifiable: the savaged Baluchi rug (does anyone know how much a tassel-less one is worth?); the Art Nouveau figurine that I was about to take to Christie's - worthless pastiche it may have been, but not even the expert would have been able to tell from my little dustpanful of fragments.

The embarrassment factor is a big consideration before you welcome these beasts into your home (let's face it, they perform DIY colonic irrigation in public). Too often I've had to smile nervously at a dinner party guest while, behind him, Devon was licking the salt off the cocktail snacks. And Tess has an underwear fetish - particularly for anything black and lacy. It's very cute to hear her hunting cry when she appears with a freshly caught bra, but less amusing when you are showing the builder round and have to navigate him through an assortment of strewn lingerie. When I explained, his "pull the other one, love" look was painfully obvious. He thought his luck was in, and kept winking at me over his paint samples. (Mind you, his quote was very reasonable.)

Also, there are behavioural problems. My behaviour has become quite irrational over the past few years. I find myself calling up the garden: "Devon Malcolm, I won't tell you again. It's supper time!" The neighbours either think I am completely crazy, or are convinced I have an England cricketer living in the shed.

Nutrition is a worry. I return laden from the supermarket, but there is never anything to eat (except for a pot of Paul Newman pasta sauce that's been lurking for months). Instead, the cupboards bulge with delicacies such as "Arthur's Chunks in jelly with salmon, shrimp and added Omega 6 & 3 oils", "Sheba with fillet of salmon and whitefish flakes in a light jelly", "Hi Life Gourmet slices of pheasant in gravy", and Kitbits, "a moist treat with cheese and beef". Soon we'll have "fricassee of sea-bream in a light raspberry coulis, drizzled with a prawn Marie Rose sauce", but it will still look brown and glutinous and smell like something you've stepped on.

OK, so I've dished out about pounds 3,000 plus on them so far. I suppose they're grateful, in their own way, but it's so hard to tell. As a little old lady at the vet's once told me, "They do smile, you know ..."