Blinded by the Light was playing on a radio in the pig shed, near sows tethered by metal collars so tight their necks were bleeding. "Imagine having to listen to that music all night," Pearson thought. So before chaining himself next to a big pig, he changed the station to ABC Classic FM.

Classical music became his calling card, each time he crept into a piggery or battery hen farm or cattle feedlot at night. He's been arrested without conviction about 14 times, he reckons, which is likely more than any of his fellow politicians in the NSW Parliament. Certainly he's the only one hearing Mozart or Beethoven in his head while riding in the back of a paddy wagon.

Pearson, 56, is a trained bass baritone and sings me a snippet from Ralph Vaughan Williams' The Vagabond while we eat lunch at a riverside restaurant in Newcastle. He has a deep, rich voice, despite contracting a cold during his first sitting days in Parliament.

"I have a colourful background," the newly elected Animal Justice Party MP noted during his maiden speech on May 6. This morning his eyes are watering and he looks a little weary after driving back from Parliament House to Newcastle's western suburbs, where he lives in a deconsecrated​ Baptist church with two dogs, two cats and some chooks he's named after wailing Valkyries.

The idea of a non-religious gay man shacking up in the mud-grey weatherboard church made him smile. "It's a bit of a slap back" to his Catholic upbringing, he says. "It also has good acoustics. And I like gothic windows."

It's important to keep a good humour, says Pearson, who has stepped down as executive director of Animal Liberation in Australia to focus on his new parliamentary role. To liven up animal liberation meetings, he likes telling the tale of Frida the Happy Battery Hen, putting on a voice like the mother from Monty Python's Life of Brian while telling people to "piss off and go pick on some pigs".

"Sometimes people in the animal movement lack humour and they're the ones who don't usually last long," he says. Other times, he eats eggs and cracks jokes about the "Vegan Nazis".

Today the amenable chef at Scratchleys on the Wharf - a bright waterside restaurant with a weird name – serves him lovely looking vegan pasta with zucchini and mushrooms. My jewfish in sherry butter sauce is good but I suspect he has the better meal.

I tell him I have considered going vegetarian but fear being served meals consisting of three types of lettuce only. Pearson says finding good vegan fare is really only tricky in remote regional areas, when he's there visiting feedlots and factory farms.

He's been inside more farms than he can recall, sometimes with the prior knowledge of the farmer. He learnt some tricks over the years of entering rural properties uninvited: don't travel under a full moon, because you cast a long shadow; always chain yourself up at the back of the shed, so the police have to first see the poor buggers in cages.

That first time he put a bike lock round his neck was in 1995, at the Parkville piggery part-owned by then prime minister Paul Keating. Pearson was among 33 people who chained themselves to the cages at midnight and stayed there beyond dawn, when police brought in the bolt cutters and took them away.

While they were being finger-printed at the station, the state agriculture minister stood on the front steps of Parliament House and announced a forthcoming ban on the tethering of sows.

"This is when I learnt that direct action works," Pearson says. "We got nothing by talking to the RSPCA or the minister or going through the acceptable protocols."

In more recent years, Pearson's preferred method of direct action has been entering farms by convoy of minivans in the early morning. "I'm getting a bit old and it's a bit hard to get through the barbed wire fences," he says. "I needed two guys to hold the strands of wire for me to get through. When that starts to happen, you realise it's time to hand the sceptre over to someone else."

He says his new seat in the NSW upper house means that "rather than being outside of Parliament protesting, handing in petitions, having appointments with politicians, I'm in their face, I'm at their door".

But he insists those days of chaining himself to cages are not necessarily past him. "I just have to be a bit more discerning, probably not when Parliament is sitting," he says.

Do you worry you might become too settled in your parliamentary seat, I ask. "Oh no," he says. "Because I have the image of those animals in my head. They're saying: 'Get me the f--- out of here.'

"I've seen too much. I would be betraying them."

Pearson grew up in Newcastle by the Bar Beach bowling club, where his father was the grounds keeper. He says his mother taught him to look after those who couldn't stand up for themselves. His dad fished for bream on the beach at night and showed him how to kill them quick with a knife to the back of the head, to end their suffering.

Pearson later worked in a mental health crisis team, helping adults struggling with schizophrenia, manic depression and borderline personality disorders. At the age of 33, he was in a bookshop buying some holiday reading when he spied a title co-authored by Australian philosopher and animal rights advocate Peter Singer. "It covered all the issues of how animals are used – factory farming, abattoirs, the making of films, circuses. And it haunted me," he says.

"It wasn't long after that that I read a statement by [German philosopher] Albert Schweitzer, that no matter how far away and over the various hills and through valleys stands the slaughter house, if you partake of their flesh you are implicated."

Pearson pauses, then shakes his hands. "Boogedy. Boogedy." For someone who freely quotes philosophers, he doesn't seem to take himself too seriously. He's a practical vegan and a practical politician – someone who says he's willing to work with the Shooters & Fishers Party, if only to win a ban on battery hens.

He says he looks forward to a future when killing an animal, for any reason other than stopping their pain and suffering, is outlawed. But he's prepared to go slow, starting with his spot on a new joint parliamentary inquiry into "puppy farms". "People have put me into Parliament to get constructive, measurable outcomes for animals, not to be dreaming of a utopia where animals are wandering about," he says.

"If we let all the pigs out and the chickens out, we would have some problems. You have to be incremental and cunning, like a fox."

I ask him what image of animal abuse haunts him most. He tells me about having to watch footage of a fox in a fur factory, quivering in the corner of its cage. "You can just see that fearful look, trembling with his eyes open and shaking and absolutely terrified. And he knows he's going to be the last one."

At such times, he turns to music for healing and relief. He tells his animal liberation colleagues to imagine themselves as Wagner's Valkyries, riding down and rescuing the sick and injured. Battery hens become so conditioned to confinement they have to be carried from their cages, he says.

"I tell them to look for the one who is on the bottom of the pecking order and save her," he says. "You can't save them all – we might be in a shed with 35,000 hens. It's terrible when you've got to turn your back on the others."

On dark days, Pearson says he might play Mussorgsky's Songs and Dances of Death, where Death is depicted as an army officer after a bloody battle, commanding the fallen from both sides. "The battle ends and the music stops, and then Death arrives and he announces 'I have won this battle. You are mine. And I will remember you when you are all forgotten by everyone. I will remember you,' " Pearson says.

"That's one piece that is very good for me. I will let myself cry and be upset and not think that's weak. I will keep going."

LIFE AND TIMES
1959 Born in Casino, NSW. Schooling at Marist Brothers, Newcastle.

1983 Registered as a clinical acute adult psychiatric nurse specialist, starts vocal training as a bass baritone.
1995 Leads a "sit in" at Parkville piggery, chaining himself with other activists next to tethered sows.
1997 Appointed team leader of the Newcastle Community Mental Health Service.

2002 Appointed executive director of Animal Liberation in Australia.
2003 Releases vision of sheep mulesing in NSW, sparking calls for a global boycott of Australian wool.
2005 Launches a national cruelty hotline, prompting police investigations into farm animal cruelty cases.

2013 Launches first drone in Australia to be used for gathering evidence of animal cruelty.
2015 Elected to the NSW Legislative Council as Australia's first Animal Justice Party MP.