CASTING the fly in salmon fishing is a complicated business. I’ve been standing on a boat in the River Tay near Dunkeld for 25 minutes now, flicking the rod this way and that, mostly getting the line in a right fankle. The ghillie, Jim, who has been doing this for 60-odd years, offers gentle words of advice. I run out of patience more quickly than I had expected and hand the rod to my counterpart, the writer Louise Gray, who gets stuck into the task with a skill and enthusiasm I just can’t muster.

When I ask myself why I’m not really enjoying my first ever fly fishing experience one word keeps coming into my head: hypocrite. If we catch a salmon – unlikely as it seems with me in charge of the rod – and are allowed under licence to keep it, someone will have to kill the creature. Frankly, I don’t fancy doing that bit. I would happily eat it, pan-fried in a nice bit of butter with some capers, but would find the process of bashing it on the head, breaking its neck, or whatever one has to do to ensure death, thoroughly unedifying.

So, there we have it: I’m a hypocrite. I would point out, however, that unless you’re a vegan there’s a fair chance you, dear reader, are a hypocrite too. Like me, you probably pay lip service to farmers’ markets and sustainable fish stocks, free-range chicken and grass-fed cows, ethical treatment of animals and fighting climate change. But when you’re tired, stressed and starving on the way home from work, and you pop in to the local takeaway – or indeed the big supermarket chain that sells you four chicken breasts for £3 – these concerns miraculously disappear.

Perhaps it’s because food is one of life’s few simple pleasures. It is also, of course, one of the most industrialised commodities in our modern world, and that’s probably where the disconnect occurs between what we eat and where it comes from, the reason so many of us struggle to associate the ham in our sandwich with the living, sentient creature that was born to be killed and eaten by us. Think about it for too long and that melt-in-the-mouth spring lamb becomes a tad less appetising, doesn’t it? And what if you actually had to kill that wee lamb yourself. Would you? Could you?

That’s exactly what Gray – currently mastering the fly fishing with aplomb – decided to find out. Fed up listening to friends claiming to care about where meat comes from, for her the logical answer to being more ethical was to take the argument to its extreme and eat only animals she had killed with her own hand.

The book she wrote off the back of it, The Ethical Carnivore, provides a fascinating insight into not only what it feels like to look into the eyes of an animal you are about to kill for the pot, but also the flip side of meat-eating, the huge and complex modern food industry – the industrial sized chicken, pig and salmon farms and associated issues around land management – that allow us to eat it cheaply every day of the week if we so desire.

Thankfully for all the hypocrites out there, the book is neither preachy nor lacking in laughs. Gray, who lives in Edinburgh, writes with humour and humanity, inviting us to share her experience of events few would have the stomach for – a visit to an abattoir, killing and butchering a pig by hand, stalking and shooting a stag.

At the very least, the book makes you think about where food comes from; it might even lead you to modify your supermarket trolley. Gray herself was changed by her experiences, but not always in the manner she expected.

“Obviously it transformed the way I eat,” the 38-year-old tells me as we sit in the boat waiting for the salmon to show up. “I eat many more vegetables than I ever did before and I feel and look so much better for it. I’ve also learned how to cook good vegetarian food.”

Gray grew up on a farm in rural Essex to Scottish parents and was already at home with country pursuits when she came up with the idea for the book. But the killing precipitated more complex feelings than she had anticipated.

“There was a point after I’d killed a pig when I swear could smell it – the blood, the gore – every time I went down the meat aisle in the supermarket,” says the journalist, who was The Telegraph’s environment correspondent for five years. “I used to get flashbacks and that was very strange. But it didn’t make me a vegetarian or a vegan, which I sort of assumed it would. It just made me think very differently about where food comes from.

“There were times when I felt quite stressed and pressured, but I wanted to understand what it was like to kill an animal. That was tough, but I kept going and I met some amazing people, gamekeepers and fishermen, who know and care so much about the land and the animal they are hunting.”

The project also prompted Gray to examine the intellectual reasoning behind what she was doing – the list of animals she has killed so far includes various types of fish and shellfish, rabbit, squirrel, pigeon, pheasant, deer and pig.

“Doing what I did can’t help but make you ask deep philosophical questions about how we look at death, how we connect with animals and, ultimately, what makes us human,” she explains. “At the beginning I got very obsessed with death, how we cope with the death of an animal, how humans manage to somehow cut it off in our brains.

“When you kill something for the first time you take on a responsibility. I felt guilt and I still do to some extent. All these animals are still with me in a way. The rabbit was the first and afterwards I felt like I’d taken on a dark reality that I’m not sure I’d have chosen to take on if I wasn’t doing this.

“Writing this book made me more resilient as a person, though. I’ve had to face my fears and make sense of difficult issues – I’ve grown up.”

Unexpectedly, the book also gave Gray the opportunity to augment her relationship to her farmer father, Duncan, who originally comes from East Lothian. Gray was just three when her mother, Marianne, died of a pulmonary embolism at the age of 29. She went to boarding school in England, then university in Manchester, but says she always felt very close to her Scottish roots – “I didn’t have much of a choice really – my dad always talked about Scotland as the superior country.”

Like many farmers, Gray’s father and brothers are keen stalkers, but she says she was initially reluctant to involve them in the book. Eventually, she changed her mind.

“I thought stalking a stag with my dad would be too loaded, for the same reasons you don’t want your parents to teach you how to drive,” she laughs. “I thought he’d be judging me. But If I was going to be honest about how I felt about killing, then I was going to have to be honest about the family issues in the background, and deal with them.

“Despite growing up on a farm I’m not confident around guns, but I had to overcome that. I built up slowly by shooting rabbits. By that time I realised Dad was capable of taking me stalking, and I was capable of doing it with him. We had more of an adult relationship. I really wanted to go stalking with him – he’s a great stalker and it is a really big part of who he is. I wanted to see and enjoy that part of him.”

In the end the father and daughter went stalking together on Ben Damph, an estate in the northwest Highlands partially owned by the Gray family. It was clearly a special moment for both.

“It was a huge privilege to go up on the hill and see the stags rutting, to smell them and understand their life,” says Gray. “My dad knows the land so well and so do the stags. But it’s important to realise when you are pointing a gun at a stag that no matter who else is there you are essentially doing this alone. To go with my dad was amazing, but I shot the deer – I chose to do it.

“I’m not sure I’d want to do it again. It’s all about accuracy – that was all I was concentrating on. I didn’t feel sad, though I remember wondering whether I should tell people that I did. In the end it was quite businesslike – I felt gratitude that I’d done it OK and not made a mess of it. I felt a defiance to protect myself – I’d gone against nature in a way, but I had made that decision. I still feel that defiance now.”

And what does her father think of the concept behind the book?

“He’s been very supportive of it all,” she smiles. “I also realised that he is already the ethical carnivore. I’ve never seen him eat chicken. My step-mum told me they don’t buy it because the chicken we get in supermarkets is only a few weeks old – my dad says there’s simply no point to it.

“You imagine some of these hunting, fishing macho types would eat nothing but meat, but they don’t. And they certainly don’t eat much meat from the supermarket – they don’t even really see it as meat.”

Going to an abattoir to watch the factory-scale death of animals, was challenging in a different way to killing them with her own hand, Gray admits.

“I remember asking myself what was it about the experience that was so awful, especially since the animal dies in a second,” she explains. “I think it’s because you are out of control. You are seeing what humans do to animals on a massive scale and it’s in your face, there’s no escape. Once you’ve seen it, you are forced to try and work through it in your mind. That’s difficult for your heart and soul.

“Our grandparents knew how pigs were killed – my granny doesn’t see the point of this book at all. But most people of my generation wouldn’t have a clue. That’s why there is a demand for information and this type of book right now.”

This exploration of how and why we have become so detached from the food we eat has certainly caught the zeitgeist as society simultaneously eats ever more processed meat in a zombie-like fashion and demands more information about provenance and animal welfare. But how did we get here in the first place? As Gray points out, only a couple of generations ago meat was a rare and expensive treat.

“I guess when people move away from the country to cities and towns we automatically become disconnected,” she suggests. “And, of course, it works for retailers for us to be disconnected. If we wanted to know everything about chicken welfare, the chicken would be more expensive, so maybe we wouldn’t buy them.

“But we’ve hit a philosophical wall. People are more concerned with welfare, but don’t really want to think or talk too much about it.

“Caring about animal welfare is one thing that makes us human. I’ve never come across anyone who says ‘we need to feed the world and it doesn’t matter how badly we treat animals’. We just need to have more open conversations about what we find acceptable. And I think we’re moving towards this.”

Gray believes as more people become aware of issues around the environment, land management and food production, consumers will increasingly turn towards meat alternatives such as Quorn.

“Farmers sometimes get annoyed with me for writing the book,” she says. “They think saying people should eat less meat will harm them. But they’ve got the best meat in the world. Encourage people to buy an Aberdeen Angus steak that has been raised on the hills every now and then rather than cheap pork three times a week. This approach works in favour of Scottish farming, I think. But it’s a complex issue.”

Gray’s year of killing is now up. She is trying to stick to the principles she learned as far as possible, but admits slipping back into bad habits is all too easy and talks of struggling to resist cheap fast foods.

This honesty and lack of worthiness, this insight into human weakness, is, for me, the most enjoyable aspect of Gray’s book. Some of the things you read about in The Ethical Carnivore make you feel bad – but Gray herself never does. This humane attitude to both people and animals is reflected when I ask her what individual consumers can do to help animal welfare and the environment.

“I’m cautious of telling anyone how to eat,” she answers. “I can only really tell my own story. The easiest thing is to eat less meat, I suppose, if you can. I’d also suggest buying from farmers’ markets, open-farm Sundays – connecting with farmers can be such a joy. And celebrate the meat you do eat – cook and enjoy it in the best you can.

“I’ve learned that being negative doesn’t work. Better to tell a positive story and encourage more positive behaviour, to tell people the wonderful things about Tamworth pigs than the bad things about Danish pork.

“I wouldn’t judge anyone for feeding their kids chicken nuggets. That might sound ridiculous after writing this book, but I try to have a bit of humanity about these things – life takes over and life can be very difficult. If we say you have to be perfect, nothing changes.

After hours of casting our flies in glorious autumnal Perthshire, we admit defeat and take the boat in; the salmon have beaten us. Am I relieved we haven’t caught anything? Spending the day with Gray has opened my mind to new ways of thinking about our food and I’m actually quite disappointed now that I won’t get the chance to test my own hypocrisy. Maybe I will visit a farmers’ market instead.

The Ethical Carnivore: My Year Killing To Eat by Louise Gray is published by Bloomsbury, £16.99