The first person he had sex with after his breakup was Rowe.

But it was a week after the diagnosis, when he returned to the clinic, that a consultant asked to see him after his scheduled appointment. She told him to sit down.

“She said, ‘I wanted to let you know there’s been four other cases in these surrounding areas saying the same exact thing you said – a Scottish guy, phone calls – and they all have HIV. We strongly advise you talk to the authorities right now.’”

Oliver knew exactly what he wanted to do. “I said, ‘Get them on the phone right now.’” That decision led to a case that would make legal history. It also led to the police catching Rowe: Oliver gave the officers Rowe’s address.

The police also came round to Oliver’s house and later filmed an interview with him, part of his testimony that would later be played in court. One of the investigating officers used videos to identity Rowe by showing Oliver a selection of men, of which one was the suspect.

“He [Rowe] came up,” said Oliver. “I knew – he was smirking.”

When initially questioned by police, Rowe denied everything: denied ever meeting Oliver, denied meeting people for sex on Grindr, and denied being HIV-positive.

But it was a lie that was provable even then. While investigating Rowe, BuzzFeed News discovered a comment written by Rowe under a YouTube video. The video was about an unsubstantiated alternative health regime called “urine therapy”, in which proponents of it drink their own urine to cure a range of conditions.

In April 2015, Rowe wrote under the video:

“I was recently diagnosed with HIV... I have been drinking my morning urine for few weeks...Anyways any more advice you can give me to heal myself from this virus would be amazing thanks x.﻿”

Rather than take antiretroviral drugs – which are proven to not only successfully treat HIV but also make it impossible for the individual to transmit the virus – Rowe had rejected medical science. He had become an AIDS denialist, a member of a tiny fringe minority who believe HIV does not cause AIDS and that the treatment is just a conspiracy by pharmaceutical companies.

Under his comments, others, including the person responsible for the video, encouraged Rowe to continue. Some told Rowe it’s not true HIV causes AIDS, and that drinking urine, not drugs, is the answer.

Six months after posting that comment, Rowe was inside Oliver’s house in Brighton.

Oliver looks up and stops for a moment to explain why he is sat talking to a journalist and why he went to the police.

“Now I have it [HIV], I best do something with it and help other people,” he said. “I will do what I can to make sure he goes to jail.”

But his determination to secure justice, it transpired, was not fuelled by revenge, but by the very impulse that ensured Oliver had worn a condom throughout his adult life: the protection of himself and others.

“He made a decision, but he’s not going to change my life,” said Oliver. “I’m going to continue my life. I’m not going to be a victim. I’ve never been a victim. I come from a shit childhood, what I had to go through to let some little twat think he’s changed my life? No.”

The shift in Oliver’s attitude, however, to fight rather than sink, had been swift and very recent. As he sat in that hotel room three weeks before we met and contemplated the box of sleeping pills, something shook him. He described it like waking up – a thought slapping him: What are you doing? He told himself he was being stupid and forced himself to go for a long walk.

“I decided no one’s going to win or be in control of my life – it’s going to be me,” he said. “I’m going to have that positivity. Always.”

Nineteen months later, Oliver walked into the courtroom at Lewes crown court. Dark wooden panels and benches adorned the square room. A yellow and blue stained-glass window hung above. The only flash of modernity was a huge flatscreen TV aside the judge to show the jury videos of police interviews. BuzzFeed News sat on the press bench with several other journalists.

Rowe, who had been on remand for months, was brought up, looking flushed and anxious. His previously sharp, lacquered quiff now sat oblong and fluffy – a prison cut.

Along with the other nine men giving evidence, a heavy curtain was pulled across the witness stand so that only the judge, barristers, and jury could see Oliver: Rowe could not.

Instead, the defendant sat in the dock in a navy suit, motionless, expressionless, as Oliver’s testimony unfurled.

Caroline Carberry QC, the prosecution barrister, began to question Oliver, establishing the circumstances in which he met Rowe: the conversation on Grindr, Rowe turning up at his house. The sex.

From the witness stand, Oliver repeated what Rowe told him: “I got you. Did you feel my come come out your arse?” And, he said, as he had told BuzzFeed News the year before: “I ripped the condom, so burn.”

Carberry asked what Rowe’s tone of voice was like. “He was kind of laughing,” Oliver said, as his voice cracked for the first time. Until that moment he had sounded composed and confident – as if mustering all the dignity he could under the circumstances.

He began to describe the panic he felt as the calls with Rowe revealed what had happened, and then the flu-like symptoms that raged a few weeks later.

Throughout the exchange, Rowe looked down. He continued looking down while the rest of Oliver’s recent sexual history was brought up: who he had sex with around the time he met Rowe, what the sex was, whether a condom was used, whether they were HIV-negative or -positive. “Did you have anal intercourse with anyone else in this period?”

The defence barrister Felicity Gerry QC took over to cross-examine Oliver. Her style and demeanour could scarcely have been more different. Where Carberry was clipped, precise, and factual, Gerry was dramatic, apparently friendly, and almost casual, as if exuding a breezy “one of the people” air.

“I’m not going to criticise you for casual sex,” she told Oliver, as if perhaps that would have been acceptable. That was shortly before she inquired whether Oliver was a “regular” or “prolific” user of Grindr, and what picture he put on there. Whether it just showed his face. Whether it was “sexy”.