When Greggs unveiled a vegan sausage roll in January of this year it created a stampede which took even it by surprise.

Not only did it contribute to a remarkable 58% rise in its profits for the first half of 2019, it pointed out to the nation that 'going vegan' was now not only relatively easy, but was firmly established as a mainstream dietary - and, by its very nature, ethical - choice.

A diet and lifestyle once thought extreme has helped fuel one of the biggest consumer growth points, with restaurants, fast food outlets and supermarkets all jumping on the bandwagon.

And, according to the Vegan Society, by 2025, a quarter of us will be either vegan or vegetarian.

So just what is driving this sea change in the way we view animal products?

"I can't say I'm surprised because the vegan logic is extremely strong," explains Adrian Ling, a man described as the 'Vegan Willy Wonka'.

He is head of Folkestone-based Plamil, a company which, back in the 1960s, delivered the first commercially available soya milk - a staple for vegans ever since - and has since specialised only in vegan-friendly products ranging from chocolate to mayonnaise.

A vegan all his life, he adds: "I describe it as an important and intrinsic part of sustainability.

"As we move forward it forms a very strong part of that issue and contributes to solving many of the problems."

Mr Ling acknowledges there are environment issues related to some vegan food production, but its current popularity is being carried on a wave of more sustainable food production.

His father, founder of the firm (Plamil takes its name from its original product – Plant Milk), was Arthur Ling, a man who was "vegan before the word was coined" back in 1926 when he saw a fish being hit over the head while on holiday as a child and vowed to himself never to eat flesh again.

Indeed, Mr Ling senior was one of the founding fathers of what became the Vegan Society.

But it is one of the most modern inventions, his son believes, which has changed the landscape.

"What has helped is social media," he explains.

"Once a certain cohort of people, start to follow a vegan diet generally others think along the same lines.

"More products become available and its accessibility is also greatly improved.

"And then you get into a cycle of commercial companies being able to sell more product and then you have a strong economic factor coming in which propels it even further."

Maria Chiorando, a former Kent journalist and now editor of Plant Based News - a website which attracts some 23 million visitors a month worldwide - agrees that the ease of access to information is fuelling the boom.

She says: "Social media, and the internet in general, have been key in the growth of veganism in the way they democratise the sharing of information.

"A key factor is the general public's growing awareness around the devastating impact animal farming has on the planet.

"The most comprehensive study around the impact of food production - published last year in the journal Science - showed that ditching meat and dairy is the most effective step you can take as an individual to reduce your impact on the planet.

"As a result, an increasing number of people are adapting their diets, which is leading to an increase in vegan food products and attention around them.

"Growing awareness around farming practices, the growth of online 'influencers', and interest in the health benefits of a plant-based diet are all factors too - as well as initiatives like Veganuary, which encourages people to try a vegan diet throughout January.”

But while fast food chains cash in, there's been plenty of criticism over the long-held beliefs that veganism is a healthy option.

Adds Mr Ling: "There are concerns that in the same way people who have a burger everyday are then surprised their diet is not providing them some nutrients, that may well happen on a vegan junk food diet as well.

"A number of years ago, people would enter veganism and they would have to go and find out about it.

"They would have to take a bit of interest in nutrition and trip over a bit of information here and there and therefore they were more informed about nutrition generally.

"I think there is some concern bubbling up when I speak to my generation of vegans is that access to veganism and the marketing of some vegan foods could lead to accusations the vegan diet is not as healthy as it once was or is as equally unhealthy as some of the junk food - not because its vegan, but because people aren’t taking notice of nutrition."

But as the likes of McDonald's, Burger King and KFC launch vegan products, is there not a clash of conscience over spending money with firms whose fortunes have been made on the back of the mass slaughter of animals?

Says Mr Ling: "I would be concerned that the commercialisation in the market is chasing the vegan pound and, historically, brands chase it and then spent that profit in other non-vegan ways to support non vegan brands.

"The argument is we should support these brands and it will encourage them to do more product.

"It's a double-edged sword and there are a few brands I could name, where people have said they have a fantastic new vegan product and after a couple of years it has strayed back to promoting non-vegan foods."

While Mr Ling is very much of the 'broad church' vegan philosophy, it is the sometimes militant faction which sits uncomfortable with many, not to mention the recurring joke: How do you know someone is vegan? Don't worry they'll tell you.

He adds: "Is veganism a religion? I don't believe it is - but it acts like one sometimes.

"There are different factions. I personally resist this whole statement that 'I am a vegan' because the definition of veganism is a lifestyle that chooses to avoid.

"It's segregated into dietary terms, but how far do you go? I personally couldn't say honestly, or of anyone I have ever met, that you completely succeed in it.

"I believe it's a journey towards an ideal and in this vegan movement you get a lot of people that are starting out with a dietary requirement and others further down the thought process and have changed their lifestyle in accordance with that.

“They could then be seen on the more extreme end of the scale. But I don't think it negates anyone's contribution to it.

"Personally, it's the number of vegan meals eaten rather than the number of vegans that are around I celebrate.

"Social media, and the internet in general, have been key in the growth of veganism in the way they democratise the sharing of information" - Maria Chiorando

"I welcome every step towards less cruelty to animals and that school of thought."

Plant Based News' Maria Chiorando adds: "While I can't speak for all vegans, I would certainly embrace anyone who is consciously making positive changes.

"Also, there are lots of people who go plant-based for health and end up vegan for ethics.

"Veganism isn't a diet, but a philosophy, which, as per The Vegan Society's definition, is about doing what is 'practicable and possible' in pursuit of this goal. Unfortunately, perfection is impossible.

"I stopped eating meat around nine years ago, after I adopted a cat. The experience made me appreciate how sentient and unique animals are.

"With this in mind, when I then read a statistic about how many thousands of animals are slaughtered every second for food, I no longer thought of them as an unquantifiable mass, but as individuals.

"In this context, the scale of the unnecessary suffering was overwhelming.

"When I came across information about the dairy and egg industries a little while later, and realised how exploitative and abusive these are, I decided to commit to veganism that day.

"Society makes an arbitrary distinction between the animals we choose as our companions - like cats and dogs - and those we have decided it is normal to eat.

"But in reality, there is no difference in their capacity to suffer, or their right to not be abused and exploited.

"We have no need to eat animals, we can live very healthily eating just plants, and yet in our pursuit of animal foods, we treat living creatures like units of production.

"When you learn that cows can play fetch if you throw a ball for them, that pigs will spend a long time making their own beds, or that chickens purr when you stroke them, the line we draw between the animals we love and those we use becomes even more absurd."

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