A Twitter follower asked me if I was a vegetarian following an idle tweet about nut burgers yesterday, then presented two subsequent questions which I've often been asked in the last twenty-four years: why did I become a vegetarian, and why aren't I a vegan? (the latter query is often framed in the form "do you wear leather shoes?").

The answers are too long for the two or three sentences afforded by Twitter, so I thought I'd compose them here.

I was twenty-four years old when I first seriously thought about what I was doing by eating meat. A cousin had been vegan for a while, and that had piqued my interest. The Smiths, one of my favourite bands at the time, had recorded an album entitled Meat Is Murder. And a year or so earlier, on its opening night, Channel 4 had shown a disturbing documentary on the welfare of animals used for food.

I pondered the idea of becoming vegetarian for a while. I think the key moment was in January 1985 when, on returning home following a beer or three at a pub in Hartlepool, I dragged the New Year turkey out of the fridge and started picking at it. The ugly reality of what I was doing was suddenly clear to me: I was pulling dead flesh from the carcass of a deceased bird, and putting it in my mouth. This was something of an epiphany.

But I didn't give up meat there and then. I thought it might be too hard to give up bacon, ham sandwiches, turkey at Christmas. But I kept thinking about it and thought that I should at least try. Eventually, one lunchtime in late January or early February 1985, I removed the pieces of bacon from the top of the pizza I'd just microwaved, and decided that this would be my first meal as a vegetarian. I wasn't sure whether I'd be able to maintain this status indefinitely, and in fact it was more complicated than I'd anticipated. A lot of otherwise innocuous products like treacle pudding and wine gums turned out to contain animal products when their list of ingredients was inspected. But in fact that carefully modified pizza had been the final turning point, and I had turned my back on eating meat forever.

After a few weeks, the very idea of meat eating had become repulsive to me, in a way that I hadn't expected. There was no longer any way that I'd be prepared to put pieces of dead flesh in my mouth. Twenty-four years of eating from animal corpses in a society where it is regarded as a normal practice had desensitised me to the grim reality of it, but now I was starting to see things much more clearly. I no longer thought of meat as a kind of food that I didn't eat. I didn't think of it as food at all.

I honestly believe that most meat eaters just don't think about what they are doing. The problem is that the necessary confinement and destruction of living creatures is not really apparent in the brightly labelled packet of sausages on the supermarket shelf.

Most people, I hope, would be saddened to see a dog killed in an accident at a pet shop. Why then are the same people for the most part happy to have a pig killed for them, when they could eat something equally nutritious instead, probably more cheaply? Do they imagine that the pig has less to lose than a labrador, or would prefer any less to remain alive? Would they feel better if the dead dog were to be chopped and fried, then served between slices of bread? It doesn't make sense.

One day I'm convinced that the animal holocaust will be remembered as mankind's defining, single most enormous crime. The sheer scale of our industrialised exploitation and destruction of other creatures is breathtaking. Twenty-three million chickens are killed every day in the United States alone; hundreds of unnecessary deaths every second.

So why am I not a vegan? In fact I did give veganism a go. In 1990 I decided that I should try the next logical step, and make my lifestyle as ethical as possible, so I removed dairy products and eggs from my diet as well. Unfortunately, whereas a healthy diet as an 'ordinary' vegetarian is very easy to maintain - I've honestly more or less just eaten what I felt like - a vegan diet does need to be considered quite carefully, and I was just too lazy to do that. Friends had started to tell me that I looked thin and pale (or "fluorescent", in the words of one of my colleagues) and at the end of 1992, weary of chocolate substitute and of feeling tired most of the time, I returned to ovo-lacto vegetarianism (that's the regular, egg and dairy product-consuming variety).

So, it's a compromise to a degree, I accept that. I'm settling for a low impact lifestyle within my own comfort zone. In an ideal world, I'd have something to put in coffee without making it taste worse that wasn't extricated from an imprisoned cow. In the meantime I'll settle for the knowledge that animals aren't killed for food on my behalf, and for setting an example of a life free from eating meat that's healthy and easy.

"To animals, all people are Nazis. For them it is an eternal Treblinka" - Isaac Beshevis Singer