What makes Hetty Johnston laugh? In her role as Bravehearts founder and executive director, Australia’s most prominent child abuse campaigner recently went spruiking for support at the annual general meeting of a chamber of commerce – she declines to say which one – and told a “dirty joke”.

Johnston is sitting in her home in a valley on the Gold Coast hinterland, surrounded by hills and through which a creek runs, having just given Ian, her husband of 21 years – a tall, one-time rugby-playing Kiwi who runs a floor sanding business – a goodbye kiss for the morning.

So what was Hetty Johnston’s dirty joke? “On its own it probably sounds a bit rough [so] I don’t think I’ll repeat it,” she demurs. “It’s one that needs to be told while you’re looking at people.” She chuckles. “It requires some hand actions.”

Her audience, she says, roared with laughter. “It wasn’t filthy; more on the risqué side.”

So does the woman who earlier this year sparked a police investigation that saw photographer Bill Henson’s images of naked pre-pubescent bodies ripped from a Paddington gallery’s walls laugh often?

“I laugh every day,” she says. “I do have a wicked sense of humour.”

In this tranquil home and valley, her rare downtime is spent tending her horse, or perhaps a whole day cooking in the kitchen, maybe reading a “girly” novel or turning up Pete Murray on the stereo; it’s an oasis when the campaigning “does my head in”.

“I try to take a rational approach to everything,” she says. “Sometimes I do get irrational, I have to admit.”

This is the self-aware flip side of the woman of whom Sunrise executive producer Adam Boland once wrote to website Crikey: “Hetty is a passionate woman – which we admire. Unfortunately its been my experience that she feels many people are out to ‘get her’.”

Johnston denies any paranoia, though she did write a few years ago that former Queensland premier Peter Beattie’s media officers were “all pointing their poison pens in my direction”.

She acknowledges she comes across to some on quick nightly TV news grabs as “that angry, unqualified, nasty mother”. Not that she cares too much about her critics: every day, strangers approach her in the street, “wanting to say thank you, shake my hand, and give me a cuddle”.

Hetty Johnston is not in the broader sense a morals campaigner. In 2004, she accepted donations from adult industry companies Club X, Adultshop and Gallery of more than $4000 in her unsuccessful campaign as an independent for a Queensland senate seat.

“If I had my time again, I wouldn’t have taken the money, to be honest,” she says sheepishly. “But I did.”

She and Ian also had to refinance their 1930s home to help fund the campaign. She professes no ambition to run for Parliament again.

Incidentally, she had believed it was illegal for sex shops to stock pornographic videos: “I’ve never been into a sex shop, I have to say, so I just figured it was stuff for adults.”

It’s a surprisingly naive statement for a woman who turns 50 on September 27; she’s planning a backyard spit roast and party for 150 family and friends for her birthday.

Meanwhile she is preparing to mark National Child Protection Week – which starts on September 7, Father’s Day, to acknowledge “how important fathers are to children” – by organising her 11th White Balloon Day on Tuesday, September 9, when people are encouraged to buy a balloon to help break the silence around child abuse.

It was Mother’s Day, May 9, 1976, when Hetty Johnston gave birth to her first child; a blonde, blue-eyed girl. Growing up in Ocean Grove in Victoria, her mother had told her the Pill was a headache tablet, and Hetty, having believed her mother, fell pregnant at 16 when having sex for the first time with her much older first boyfriend.

She couldn’t deny her child the right to live, though upon learning of her pregnancy she “wildly punched” her stomach. Today, she says she has no position on abortion.

The child’s father offered to marry her, but Johnston “hated him” for not taking precautions. She gave the baby up for adoption, never having held her.

Johnston’s parents, Dutch-born Peter, a Protestant, and Frieda, a Catholic – though the family were not churchgoers – had allowed their pregnant middle child to leave home in Victoria and head for Kalgoorlie for several months with a bunch of friends, including her second boyfriend. She writes in her 2004 autobiography, In the Best Interests of the Child (Pluto Press): “As much as my parents loved me, they couldn’t get past the hurt, the shame, the anger and the disappointment they felt.”

Says Johnston now: “I absolutely adore my parents, and I see them every week at least [they retired to the Gold Coast] and I love them.

“They acknowledge – particularly my father – that they made a mistake in behaving the way that they did. But it so offended his morals. He can be temperamental.”

Did she forgive them? “Absolutely. Never held it against them.”

Johnston’s first marriage was short lived, but her second marriage, to Ian, in 1987, has proven tough enough to weather the discovery in 1996 that Ian’s father had been molesting their daughter – Hetty’s second child, Kayleen, then seven – during family visits to New Zealand.

Johnston had the police called in via Interpol. Her father-in-law Alexander Johnston, it turned out, had been abusing young girls in the family for 40 years, pleading guilty to 19 offences and serving 15 months of a three-year jail sentence. He still lives in New Zealand with his wife, Ian’s stepmother Flo, though Hetty and Ian have cut contact with them.

Kayleen, now 20, worked until recently at Bravehearts – “but she wanted to get out from under my skirt, which is really cool,” says her mother – and now works in administration at a lighting company.

Does Kayleen carry any burden from the abuse? “Well, I don’t think so,” says Johnston. “For everyone that’s harmed like that there’s always going to be something.

“I had this conversation with her recently again: ‘Hey, Kayleen, how are you travelling?’ I drive them nuts, because I check in on that all the time.”

In 1991, Johnston was reunited with her first daughter, named Anj, who is now 32, works as a bank teller and has her own daughter, Taylah, who turns nine this month. Johnston is close to both daughters and her granddaughter.

She doesn’t feel guilt over giving up Anj – “as far as I knew at the time, I didn’t have a choice” – but admits to an “ingrained sadness”. She felt guilt in the beginning over the abuse Kayleen suffered, “but if you didn’t know something was going on, you can’t then blame yourself”.

Johnston made her name by starting the campaign that eventually brought down Peter Hollingworth as Governor-General in 2003 over child sexual abuse in the Anglican Church over which he had presided in Brisbane.

She still believes in God, even if she has no kind words for the churches. “I have faith, and respect everybody’s faith, no matter what that might be,” she says.

“I was raised a Christian. Even though I don’t go to church – I just don’t, and I won’t – I know that when my time comes, if there is a heaven, or if there is a good place, I know in my heart I’ve lived by the commandments of the Bible. That’s how I’ve lived my life.”