I'm not entirely au fait with the ins and outs of the law, but if Taz, my beloved Staffordshire bull terrier, does have to be put down as a result of my actions two nights ago, I hope that the NSPCA will accept that I acted without malicious intent and will punish me for dogslaughter instead of cold-blooded murder. As I sat down to write my column, dear Taz (old Taz, now, at nine), wobbled up to my desk wagging her tail. She tried her usual trick of jumping on to my lap (she loves jumping, silly old thing) but her back legs buckled and now she sits, warming my feet with a look of knowing melancholy about her greying muzzle.

My sad tale began several years ago after I split with my fiance, who promptly went out and bought a new bed for himself. The old bed that his grandad had died in was good enough for me to lie on but not his intended new girlfriend. The message was loud and clear: new bed, new bedmates. Well, now we're married with two young children, but this squat, loathsome reminder of our time apart remains. Why? Well, money really, and the old-fashioned notion we both cling to in this wasteful world that if you've already got one - why buy another?

Besides the fond memories it no doubt holds for my husband, the most loathsome thing about the bed is its size, or lack of it. It's only a double.

What use is a double in a marriage? A double bed is an exciting alternative to teenagers whose fumblings on the single bed at home have inevitably ended up on the floor with hard-to-explain carpet burns on legs and buttocks. A double bed is great when you travel alone, when you fall into its crisp sheets after a drunken night out or curl up (alone) on one after an exhausting business seminar. Double beds are (if I remember correctly; perhaps I'll ask my husband) pretty good for all-night shagging with virtual strangers who hurriedly dress and leave before the fight for covers threatens a beautiful lack of intimacy.

Nowadays, our bed is a hill-billy raggle-taggle of children jumbled in with animals and adults all sharing one duvet, fighting for the most secure, least precarious spot. I can report from the Darby/Booth front line that our double bed is a hateful place for two western-hemisphere adults, a squalling newborn, a wriggling two-year-old and a four-stone, set-in- her-ways, determined-to-sleep-under-the-covers bull terrier to spend the night.

Currently, our newborn refuses to sleep. I have flu. My husband has two broken ribs. It was into this tense atmosphere that Taz casually blundered a couple of nights ago. Just as the baby threatened to snooze, the dog started kicking me under the covers for invading her furry leg space. With teeth-gritted near-hysteria, I moved her towards the end of the bed with my feet, knowing that this would wake her up and hoping to persuade her that tonight the sofa would be a better spot.

Instead, as I urged her further and further away, a sickening "whump" broke the quiet. My dog hit the floor. This has happened several times before - to my husband. Even clinging to his three inches of bed hasn't saved him from my need to stretch out at night. When it happens to him I start to giggle and I giggled now, waiting for the dog to sigh and huff out of the room. Silence. Taz had been dead to the world. And now she appeared to be in a coma.

We leapt into action, lights went on, a special towel appeared. Taz was lifted woozily on to the centre of the bed where she spent the rest of the night surrounded by humans clinging to whatever space was left. According to the doctor, Taz has concussion - and she also has pride of place on the bed (or my space if things get too busy) for as long as my daughter and husband keep giving me those accusing looks.