It was an intensive course of prayer, study, and worship over several months. And it was here that Venn-Brown confessed his attraction to men to the principal of the college. There was, the principal said, no option but to be exorcised.

For the next few weekends, a member of staff took Venn-Brown to a huge Pentecostal church called the Queen Street Assembly of God. Its chief pastor, Neville Johnson, was known for his divine visions and invocations of spirits.

Venn-Brown begins to relive what happened. “The minister [Johnson] and his assistant would take me upstairs,” he says – to a hall on the first floor of the church, where the chair was placed in the middle.

Before tackling the homosexuality, there were the confessions. “You had to confess any sins you had,” he says. “It’s about cleansing. I remember I confessed that I’d stolen a Crumble [chocolate] bar from the local newsagents. Anything you could think of. It was a purging.”

Venn-Brown had to confess to his forefathers being Freemasons, who were seen by this church as followers of the occult. He had to confess to masturbation.

Then they began to pray, summoning the spirits out of him.

“They say, ‘Don’t pray yourself, we’ll pray for you; you concentrate on expelling the demon.’” As he continued to confess, now admitting to his attraction to men, Johnson and his assistant began speaking in tongues. They commanded the demon to surface, raising their voices, shouting over the 20-year-old and ordering him to start breathing out. By exhaling heavily, he would help expunge the evil of homosexuality.

“What happens is you start to hyperventilate,” he says. “My hands started to close up, I started to get sensations through my face, thinking, ‘Oh my god, the demon is coming to the surface.’ Then you start to breathe more and expel the demons.” As the hyperventilating accelerated, pins and needles coursed through him as the forced breathing turned to coughing. Overwhelmed and deprived of oxygen, he fell from the chair on to the floor.

The newspaper was placed in front of his mouth as he expelled the bile that had been brought up. He spat it on to the paper.

He was, he says, dry retching. Johnson and his assistant continued calling the devil out of him, voices loudening further. “They were saying, ‘Come out, you foul spirit! Come out in the name of Jesus! Come out, you spirit of homosexuality!’” They began counting each demon as it flew out of him, with Venn-Brown remaining on the floor, coughing and hyperventilating, until every spirit was deemed to be gone.

It took over two hours. But it was not enough. Johnson told him to return the next week for more, and the week after that. “Thinking you have a demonic force inside you is not good for your mental health,” he says. But it is only later that he describes what that meant.

Initially, Venn-Brown thought it had worked. He stopped feeling anything towards men, but he knew he still had no attraction to women. And with hindsight, he says now that when his innate desires waned he wasn’t becoming less gay. He was simply becoming more traumatised.

The following year, back in Sydney, it was clear the exorcisms had failed. “The more I tried to push this thing down, it would always rear its ugly head,” he says. On the instruction of his pastor, he admitted himself to a residential unit designed to make him straight. Surely, he reasoned, this intensive treatment would work.

By now it was 1972, and what would come to be known as conversion therapy (also called reparative therapy) was beginning to emerge. While “healing” and exorcisms had been swirling on the fringes of Christianity for centuries, and while aversion therapy had been practised for decades, conversion therapy would bring together elements of all three, along with techniques bastardised from more traditional talking therapies, to form a practice, an ideology, and an international crusade: the “ex-gay” movement.

While in the US organisations such as Exodus International sprang up, in Australia it was less big business, more small churches, with Venn-Brown’s evangelical community at the forefront.

Moombara House was a large sandstone building nestled on the edge of Port Hacking, just to the south of Sydney, and run by the Bundeena Christian Fellowship.

It is believed to be the first residential “ex-gay” centre in the world, something that would later be copied in similar units across the United States – right up to the present day. But as well as gay people it also took in addicts and sex workers in an attempt to save them, too. This admission policy was also used in evangelical churches in Britain in the 1990s and 2000s: All those deemed broken were lumped, and healed, together.