Harry Johnston, knacker.

We are called knackers, but I like to think of us as the undertakers of the horse world. We're not an abattoir, where animals are killed for human consumption. Anyway, in Scotland you're not allowed to kill horses for human consumption.

We have 20 wagons out covering our patch from 7am until 7pm, from Pitlochry to Ballantrae, Dunbar and Cockburnspath. We have 6500 customers and take about 400 calls a day. At this time of year, they're mostly from farmers who have come across a dead cow or a stillborn calf. We also recover beached whales.

We deal with horses every day of the year. Around 95% of those we pick up have been put to sleep by injection by the equine vet; you'd have to be quite hard-hearted to have your pet horse shot, though it's cheaper.

We collect the horses, bring them back to the yard then send off the carcasses and byproducts for "recycling". The oil and fat renders down into tallow (for the biodiesel industry) and the rest into meat and bone meal, which is a cheaper alternative to coal in power stations and cement works.

Most of the remaining 5% of the horses we deal with have suffered a snapped leg and are in pain. These are the ones we go out to and shoot with a humane bolt gun. All our boys have a gun and have licences from Defra. The bolt goes in about five inches and death is instantaneous. Horses stay standing up even with a broken leg, so when they are shot they crash down to the ground. It's distressing for the owner so I advise them to leave the stable. A horse can live for 30 years or so, so it becomes part of a family.

I'm 50 and have been doing this since I was 19, so I suppose I'm inured to it; it's hard to explain how it feels. It's not the nicest thing to do, though we do it in the most humane way. I never look a horse in the eye because you can't let emotion come into it. Speed and precision are vital. But I park the wagon out of a horse's immediate environment because some say they can smell death.

As it's not been injected this meat can be eaten by other animals. Edinburgh Zoo, Highland Wildlife Park in Kingussie and Blair Drummond Safari Park take the horse meat to feed bears, tigers and wolves, although some prefer whole calves, because lions are strong enough to eat the bones as well. Horse bones are difficult to digest, so we pick them up again from special bins. We spray all the carcasses with blue ink so there is absolutely no doubt the meat is unfit for human consumption.

It's easy to tell the difference between horse and cow meat unless it's been made into a processed meal. Someone somewhere has been deliberately misleading the public to make a buck for themselves.

At the plant we remove the cow and calf hides and salt them to dry them out, then sell them on. Calf hides are softer than cows' and are made into things like purses and wallets; we get £8 per hide. Cow hides are tougher and are made into belts and boots; we get £18 per hide. But a horse hide isn't worth the bother because it's so thin it just tears, so it goes straight to the incinerator.

It used to be easy for Joe Bloggs to come in off the street and buy a load of horse meat for a fiver to feed his dog, but six years ago Defra tightened up the rules and now it's illegal to sell horse meat for pet food. The emphasis now is on "skin and bin".