Ingrid Newkirk isn’t sure exactly how many times she has been arrested. “Definitely a few dozen,” she’ll say, if you ask. I’ve just done exactly that, so right now the British-born founder of People for the Ethical Treatment of Animals (PETA) is running me through a sort of greatest hits of her law-baiting exploits and the jailtime they have brought her in the name of animal rights.

There was the time she invaded Vogue magazine to protest against its promotion of fur and was dragged away by two of New York’s finest – though not before she had managed to answer the office phones. “I said ‘I’m awfully sorry we’re closed today due to cruelty to animals’, and hung up." Then there was the time she found herself sharing a cell with rock star Chrissie Hynde after a protest at a Gap store in New York. “We went down to what they called the Dungeon and they gave us the vegan sandwich – which was the baloney sandwich without the baloney.” Two pieces of bread, in other words. Maybe some margarine. She laughs at the memory.

And there was the time she invaded a field in Pennsylvania where a group of men, some in Ku Klux Klan regalia, were shooting pigeons they had brought there especially. The shooting was stopped but that incursion resulted in a 15-day stretch in the same prison where in 1877 members of the Molly Maguires, a group of Irish activists involved in a bitter miners’ strike, had been executed. “I could see the spot where they were hanged outside my cell,” Newkirk says.

This story has a food angle too: thinking Newkirk’s veganism a religious practice, her warders asked her if she was allowed to eat grapes. For some reason they thought the fruit represented the blood of Christ and would be proscribed. Newkirk ate the grapes but on release she promptly brought a lawsuit on behalf of the prison’s many female heroin addicts to demand proper medical treatment. She won.

Now 70, Newkirk is still very much the public face of PETA. The organisation itself turns 40 in March – there’s a raft of events planned, though Newkirk’s tight-lipped about what and when and where – and its founder has also found time to write a book. It’s called Animalkind: Remarkable Discoveries About Animals And Revolutionary New Ways To Show Them Compassion, and as well as being informative and interesting it’s refreshingly polemic-free. It feels almost optimistic, I tell her, not at all what I expected. Is the direction of travel that pleasing where human-animal interactions are concerned?

“Totally," she says. "I mean I can look back to my childhood and the things that we grew up doing to animals are things that are just not acceptable today at all. So yeah, I’ve seen so much positive change and I know the direction it’s going in, especially in technology. In medicine we have whole human DNA on the internet, artificial lungs, you’ve got organs on a chip – you don’t have to have the patter of little feet any more in the laboratory.

"It’s considered quite old-fashioned if you’re force-feeding a rabbit. When I was growing up you actually killed a rabbit for a pregnancy test. How ridiculous. But those times have gone, thanks goodness.”

Not only that but progress is happening “exponentially”, she says, which means more and more people are coming around to her way of thinking, particularly in regard to the importance of plant-based diets both for personal health and for global environmental viability.

“Young people growing up today are disgusted at the state of the world and they want to do something that’s more progressive and kind,” she says. “The environmental crisis, ghastly as it is, has woken up so many people, especially young people. It’s rather like the Cuban Missile Crisis – they envision the end of the world and they’re traumatised by it and they want to take personal responsibility, which is always marvellous. And the options are there to make it easy.”

That’s not to say there aren’t still challenges. “We’re fighting different battles in different places. We’ve seen enormous progress with bullfighting in Spain but it’s still there. We just developed an artificial lung to replace animal lungs [in experiments] but we’re still fighting the forced swimming test.”

This test involves mice being dropped into a beaker of water and forced to swim to stop themselves drowning. It’s used to test the efficacy of anti-depressants. Earlier this month, King’s College London became the first university in the world to end the practice, though under pressure from PETA drug companies Pfizer, Johnson & Johnson, Bayer, AbbVie, Roche and AstraZeneca have also banned the test. “Those sort of stupid things are still going on, so we have our work cut out for us.”

Arguably Newkirk won the argument over the use of fur in fashion – “Our motto was ‘Fur is dead’ and fur really is dead. It’s just gone, gone, gone and nobody wants to wear it” – and there’s a long list of couture designers who have turned their back on products which involve cruelty to animals. “Chanel even has a pineapple leather hat,” she says, sounding amazed. “When I grew up I had rhino skin boots, I’m ashamed to say, because nobody tapped me on the shoulder. Hopefully this book will tap a few people on the shoulder and they’ll be grateful for it”.

Newkirk has now turned her ire on the wool manufacturing industry. “I’ve been on Australian sheep farms and I’ve seen them [the sheep] cut bloody,” she says. “The Australian sheep industry from start to finish is just a record of cruelty”. She was delighted to read recently about the wool-free vegan kilts now being made in Scotland by Slanj in Glasgow and Aberdeen-based designer Scott Wood.

China is another area of concern for her. “They don’t like any outside intervention at all and they make it extremely difficult to have a website. But we have great activists on the ground who are stopping the trucks taking the dogs to the meat markets. We have kids in school who don’t like the way bears are trained for circuses and say they won’t go and want it stopped”.

Perhaps predictably, the PETA campaign which has most captured the public imagination is the one featuring unclothed celebrities under the banner I’d Rather Go Naked Than Wear Fur. Launched in 1994 with a group of five supermodels (including Naomi Campbell, who was later sacked for, er, wearing fur), it has since featured stars such as Kim Kardashian, Eva Mendes and Italian actress Elisabetta Canalis. “Our last model for that was Gillian Anderson and boy was that an eye-catching visual,” says Newkirk.

But there have been other campaigns and publicity stunts, many of them more controversial and confrontational than a bunch of naked celebrities on a billboard. Newkirk reels off a few of the more outrageous stunts. “We used to do the fur crawl, where we would put steel traps on our hands and crawl along the pavement outside fashion shows wearing fur. And when General Motors was using animals in car crash tests we tried to meet with them but they weren’t having any of it so we eventually escalated that campaign to set fire to donated cars outside car showrooms. They said ‘OK’ and changed to computerised mannequins, the car test dummies."

Has any campaign ever backfired?

“I’ve never regretted a single one,” she says. “I’ve regretted that sometimes people were offended but there’s nothing much I can do about that.”

But doesn’t she worry that in her pursuit of animal rights she’ll stop seeing where to draw the line?

“Anything that doesn’t harm any living being is what’s acceptable, really. That’s the basic rule. If you want to show reality, it may offend people but they need to see it. You need sometimes to be hit over the head with the facts. But we’re often amusing as well as provocative. We do food giveaways, we dress up as all sort of things – when we did a campaign about not testing condoms using animals we had people dressed as condoms. So we don’t mind people laughing at us, we simply want people to look. And when they look they think and it becomes a conversation piece.”

But there’s a pragmatic side to the organisation too. PETA recently sent a consignment of fur coats to Syrian refugees, gathered from Americans who have “had second thoughts”, as Newkirk puts it. Though undoubtedly welcomed by the needy recipients, isn’t it a little odd for PETA to sully its hands with such items?

“My opinion is the animals are dead, we’re not promoting the fur industry and we have to do something with donated coats,” she says. “We’ve got a whole list of things we do with them, from using them as bedding for wildlife to giving them to refugees or people who live in the street who can’t walk into Zara or H&M and buy a coat … The animals have gone and we’re showing that only those who are absolutely desperate have any justification at all for wearing those bodies.”

Born in Surrey in 1949, Newkirk spent her early years in Orkney, where her father worked as an engineer. She has scant memories of the place though she remembers being dressed head to foot in the local knitwear and she retains a deep love of the islands. The family later moved to India and it was here she spent most of her childhood. Her mother volunteered in a leper colony and Newkirk helped out from time to time as well.

Then it was off to America, aged 18. At 20 Newkirk flirted with the idea of becoming a stockbroker – she liked maths, she explains, when I raise an incredulous eyebrow – but her Eureka! moment came when she took some abandoned kittens to a rescue centre in Maryland. They ended up being destroyed and she was appalled. She took a job in a nearby kennel, blew the whistle on the practices she saw there and became an animal protection officer.

In 1980 she met activist Alex Pacheco, who introduced her to Animal Liberation, a seminal book on animal rights by moral philosopher Peter Stringer. PETA was formed in the same year and in 1981 the organisation began the first of its many exposes, at a behavioural research institute in Silver Spring, Maryland. The case of the Silver Spring monkeys – experimented on using electric shock and restraint – became notorious. Newkirk had stepped up, and enjoyed the experience.

Four decades on, she and PETA are still fighting the fight. With concerns about climate change rampant and the number of vegans increasing rapidly – 600,000 and rising in the UK alone, and we’re only midway through Veganuary – the core message about how we use and relate to animals seems more relevant than ever and appears to be reaching more ears willing to listen. But Newkirk’s take on what PETA refers to as “speciesism” is a harder sell. As hard as the word itself is to pronounce. But if there’s a new front in the war for animal rights, this is it.

Essentially, you’re guilty of speciesism if you discriminate against a living creature based on its species.“We’re against human domination in the same way we’re opposed to sexism, racism, ageism, all these bullying points of view where you only relate to those who are how you define yourself – as a woman, as a certain colour,” she explains. “The next frontier of course is to think they’re just like us – in fact we are just one among many animals on the face of the earth and we need to be considerate and understanding.”

As ideas go, it’s an outlier and for many it’s a step too far. A PETA tweet from 2018 asking people to avoid speciesist language (example: ‘Feed two birds with one scone’ instead of ‘Kill two birds with one stone’) was roundly ridiculed. But for Newkirk and for PETA, this is the logical end point of their fight: a world in which animals are accorded every legal right that humans currently enjoy.

After all, as she illustrates in the book with case study after case study, animals can communicate. They feel and can exhibit fear, loneliness and joy. They have hearts and mouths and eyes and feet. And they can learn and co-operate. Some can even be said to have culture.

One story she cites in Animalkind tells of how four enterprising baboons in an outdoor corral at the Texas Biomedical Research Institute rolled an 18-litre drum to the wall, upended it and used it to escape, fleeing through heavy traffic. The Institute uses primates to study contagious diseases, to the animals’ obvious detriment. No wonder they made a break for it.

As a philosophical argument, speciesism certainly has merit, just as it has had its advocates throughout history. But how long will it be before public opinion catches up, and the law with it?

“Da Vinci started it off, from what we know. He said one day the time will come – I’m paraphrasing – when man will look back on what we do to animals and be ashamed. And I think future generations will be embarrassed and ashamed and say things like ‘You really ate the other animals?’ So yes, I do think this is the Dark Ages that we are just emerging from now in terms of our treatment of all the other beings on the Earth.”

Whether anyone alive now will see the end of those “Dark Ages” is a moot point, but that doesn’t deter Ingrid Newkirk. For as long as she is able she’ll be there, tapping shoulders, the boys in blue not far behind.