Cowering in the corner of a pet shop, I edged towards the door to try to escape as a stranger yelled at me. The man’s face was so puckered up and puce with anger that I feared I was moments away from being beaten to death with a ball-thrower or ham bone.

I had only popped in to buy some dog food for the spaniel and now the spaniel was hiding behind me as a fellow customer shouted abuse. The lady who owned the pet shop was trying to appease the shouting man, who had his own dog with him, a scrappy little terrier who looked as terrified as the rest of us as his owner went tonto.

And what, I hear you ask, was the issue that had set the man off on his barking mad rant? Well, it was all to do with the strange case of the Tooting fox poisoner.

I say fox poisoner. It would be more accurate to say fox and dog poisoner. Because some idiot has gone rogue in the south London neighbourhood where I live and taken it upon themselves to put poison down on Tooting Common at night to kill foxes. Sadly, a much loved dog has been killed after eating the poison, believed to be hidden in lumps of cheese.

The Labrador who died was a great mate of Cydney, my cocker spaniel, and his owner was a friend of mine. We regularly enjoyed carefree walks together. I have not taken Cydney off the lead on the Common since I found out about the sad death of her friend. I daren’t let her go near the bushes bordering people’s back gardens, where it is thought the poison is being left. We are desperately upset about this, and worried sick.

But here’s the thing: regardless of whether this poisoner is dealt with, there is an underlying problem. Foxes are becoming so rampant in some areas of London, and the authorities are doing so little about them. It is inevitable that people are taking the law into their own hands.

The foxes here run wild, they ransack bins, they eat small pets, they spread mange to dogs. They foul public areas so extensively that it begins to make no difference whether dog owners pick up their poo. They are bold and fearless, sauntering about the streets in broad daylight quite casually. Sometimes, there are easily more foxes than people walking the pavements by my house. That cannot be right, and it is certainly not natural.

They are not meant to be in our habitat. But they have been encouraged by people feeding them. A few years ago, I was taking a black cab home when the driver wound his window down, reached into the passenger footwell, and started throwing Wall’s sausages on to the Common. I urged him to desist, but he said foxes were wonderful creatures. And that is what we are up against.

Every day, I sit in my study at home with foxes screaming outside my window. They come up the path to my front door and screech for food. They no longer run away when you approach them. In summer, they come through open back doors. And you cannot do anything, because attacking them is forbidden. They have more rights than us.

And the authorities seem happy with this. I once rang Lambeth council to ask for advice on the issue and they sent me an RSPCA leaflet explaining what to feed foxes — they particularly like chicken pieces, apparently. Although they’re also partial to a pet rabbit or two, in my experience.

The mayor, Boris Johnson, makes noises whenever babies are attacked about doing some kind of cull. But no action has been forthcoming.

And so there I was, standing in my local pet shop chatting with the owner about how terrible it was that our friend’s labrador had been poisoned by someone sent half mad by the fox problem, and how this showed that the council should do something, when a man entered with his dog and began to shout: ‘You can’t kill foxes! You’re not allowed to kill foxes! No one has the right to kill foxes! No one!’ And he went on screaming about the rights of foxes until I edged backwards out of the shop, sensing that the animal rights nerve had been activated.

Later that day, as news spread like wildfire about the Tooting poisoner, a friend who also walks her dog on the Common rang me in a panic. She lives in the street where it is thought the poisoner resides, and there were very dark murmurings there. ‘I’m really scared,’ she said. ‘People are talking about finding the poisoner and making him eat poison.’ Everyone in her street was under suspicion as the net closed in. The reality was probably that more than one resident was putting poison down in their back gardens where they joined the Common, she said. But the Tooting Poisoner had gained almost mythical status and people were hysterical.

She suggested we stop discussing the fox problem with anyone, for fear of reprisals. Anyone who so much as suggested that the poisoner might have been acting out of an urge to defend his property might be subject to abuse, or actual physical attack.

This was ridiculous. I decided to contact the local authorities. But a Wandsworth council press officer emailed me a response which was almost as hysterical as the man in the pet shop: ‘As a dog owner myself I certainly hope its (sic) not true — and if we receive any evidence whatsoever that it is happening we will do everything we can to catch those responsible and prosecute them — and urge the courts to impose the toughest possible sentence.’ Life imprisonment, perhaps?

I asked him what residents ought to do about the fox problem. He sent me the council’s official guidance, which was for householders to secure their bins. That was all.

I contacted Lambeth council, but they didn’t get back to me. They’re probably too busy producing more leaflets with yummy chicken recipes for Charlie.

I rang the Metropolitan police and their reaction was even scarier: ‘You need to call the RSPCA,’ said the lady there. ‘Oh god no,’ I said, and I tried to explain that I wanted help from the proper authorities to advise residents on the apparent death threats being made. I did not want a million pounds of little old ladies’ money spent pursuing one bloke who had put down a piece of poison-laced cheddar. Because then what? The problem would not go away. I tried to explain that it was a triple whammy. Whereas we used to live in fear of foxes, we now live in fear of foxes, fox poisoners and fox poisoner prevention vigilante squads.

But the lady at the Met was unimpressed. ‘Well,’ she said, philosophically. ‘This sort of thing happens from time to time.’