My cat, Biffo, does an excellent impression of a car alarm, usually when I have to remove him from his favourite sleeping place, my computer chair. He retaliates by striding up and down the landing outside my work-room, going, 'Waaaa! Waaaa! Waaaa!' in a shrill, rasping, repeated wail which bores through my concentration in seconds. Throwing things at him distracts him only for a moment. Closing the door means louder wails and scratched paintwork. Shutting him in the yard means that he batters the patio doors with both paws, rattling them in their frames, still howling, until you'd swear looters were breaking in. He's a large and determined cat.

 The only thing that shuts him up is allowing him to jump onto my lap. (Sometimes he's too idle to jump and waves his front paws at me, demanding to be picked up). Once on my lap, he settles comfortably, front paws folded under, assumes a smug expression, and vibrates gently with contentment. He watches the screen as I work, ears pricking with interest as it shifts and flickers. Happily, he's never shown any interest in getting closer to it, though once, when I printed off a book proposal, which showered from the printer onto the floor, he sprang from my lap and killed all the pages. (Critics! They're everywhere).

 Working with a cat on my lap means having to type round a pair of hot, silky little ears, and occasionally having a thick, furry tail wafted across my face, or coiled round my neck like a boa. It means having to stop and wait while the cat stands up, turns himself round two or three times, and then drapes himself across my legs like a heavy, furry scarf. But he's quiet - apart from some snoring - for hours, so it's worth it.

The next time I'm asked one of those questions - 'Do you write by hand or computer? Pen or pencil? Blue ink or black?' - I'm going to say, 'Personally, I always write with a cat.'

Biffo's a Londoner. His first can-opener, Frank, lived on the Tottenham Court Road, and was asked by a neighbour if he wanted a cat. A young Biffo was delivered a few days later, and soon had Frank under the little iron paw.

Frank named him 'Biffo' because when he fought other cats – and in those days he fought them often – he sat on his back legs, and biffed them with his front paws. Biffo was, in those days, the biggest, strongest, fiercest, roughest, toughest cat in Tottenham. He was, in fact, The Great Beast of the Tottenham Court Road. But that was nearly twenty-two years ago.

Frank had to leave London, and couldn't be sure that he'd be able to give Biffo a home any longer, but couldn't bear to abandon him. So Biffo moved on to his second can-opener, Frank's friend Davy, who lived in Birmingham. In no time all, Davy was ruled by 'the wee man in the fur suit'. To this day, he firmly believes Biffo to be the wisest and most learned cat who ever lived.

It has to be said, Biffo's street-wise, since he's survived both the Tottenham Court Road, and some of the busiest roads in Birmingham.

I first met Biffo when I went to visit Davy, and Biffo was sitting on the table, bolt upright, ears pricked and fur fluffed out in a mane and 'shirt-front', fixing me with big golden eyes. I said, “Oh what a beautiful cat!” I've found that this is usually what people say when they meet Biff for the first time. Either that, or, “What a big cat!”

When Davy had to move house, to a place where he couldn't keep Biffo, I did the noble thing, and said Biff could come and live with me. I didn't even like Biff much at the time, since he'd always made it very clear that I was an intruder. He used to climb on Davy's lap, make himself comfortable, and sneer at me.

But it didn't take Biff long to make a complete conquest of me too. So now I'm his third can-opener. He sleeps on my bed every night, and wakes me every morning by yowling in my ear. If the day's sunny, he goes out and begs food from my neighbour, and then basks on the roof of her shed. If it's rainy, he sits on my bedroom windowsill and watches everything that goes on in the street – in between sleeping on my bed, or on my lap as I use the computer.

He may be old, but when he had to go to the vet recently, they were astonished at how fit and strong he was, and I hope he has a good few years yet.