My gangster cats grow fat on the indulgence of my neighbours

Our cats are supposed to be on a diet. Ronnie and Reggie (so named because they are brothers from east London with criminal tendencies) have gone beyond nicely rounded. They look like a couple of enormous powder puffs on legs.

On vet’s orders, I have put them on a slimming regime. No more than two lowcalorie sachets a day, however much they nag and whine and dash themselves to the ground drumming their little furry fists. And yet, after six months of Spartan discipline, their waistlines haven’t budged an inch.

I know who’s to blame, although I don’t know her name. I can smell her whenever I kiss the cats on the head: Roger & Gallet’s lavender water. I recognise it from my Great Aunt Betty. Somewhere in our neighbourhood, a sweet old lady has fallen for our cats.

The same thing happened to poor Shirley Key. The 79-year-old from Kent started feeding a neighbour’s cat last spring. Unlike Ronnie and Reggie, this was a slender little creature: Mrs Key told herself that it must be a stray, or at least neglected. She fed it up, bought it toys and even paid a £200 vet bill.

And then, last month, the police appeared on her doorstep, accusing her of “cat theft”. After a stern talking-to, Mrs Key agreed to stop feeding the animal. But every time she left her back door open, he would saunter back into her house.

Three weeks later, she got another police visit: this time, they served her with a Community Protection Order forbidding her – on pain of an £80 fine and a criminal record – from allowing “any other person’s pet into her property”.

It was devastating, says Mrs Key. “I lost my brother and I’m the last one in the family, so the cat really did heal the aching in my heart.” Besides, what was she supposed to do? “Cats go where they want to go; he decided to come to me.”

This is one of the best, and most annoying, things about cats. They have social lives of their own. Like Regency aristocrats, they spend most of their waking hours promenading about town, dropping in here and there for tea. They are ruthlessly selective, never staying anywhere out of mere politeness. If a cat wants to spend time with you, it means you have been chosen.

Who wouldn’t be seduced by such flattery? To have this most discriminating of animals purring on your knee, or flopping at your feet demanding to have its tummy tickled; what better cure could there be for an aching heart?

So I have great sympathy for Mrs Key. And some, even, for Mrs Lavender Water. It is harder to see how she justifies feeding our corpulent cats – although Ronnie and Reggie are (like their namesakes) difficult to refuse. I once got a phone call from a woman four streets away, complaining that Ronnie had “shouldered his way” into her house, like an overzealous bailiff.

You can’t stop your cats loving other people, or being loved in return. But there are limits.

Recently, Reggie disappeared for two nights. I walked the streets in my dressing gown calling his name.

I wept with anxiety in case he had been squashed or cat-napped. And then suddenly, in he sashayed – as fat and groomed and scented as an Eastern potentate.

Love isn’t always kind. When it comes to pets, it can be downright unneighbourly. follow Jemima Lewis on Twitter @gemimsy; read more at telegraph.co.uk/opinion