It’s a pop fact that four of the top 10 bestselling singles ever in Britain were written and performed by gay men: George Michael (at No 9 with Wham’s Last Christmas); Freddie Mercury (No 3 with Queen’s Bohemian Rhapsody); Elton John (No 1 with Candle in the Wind). The fourth is Holly Johnson, leather-clad singer of Frankie Goes to Hollywood, whose libidinous banger Relax sold over two million copies, and is still the sixth biggest UK single ever.

“I feel quite humble that I’m among such illustrious company,” Johnson says, his scouse accent undiminished by decades down south. He’s in the function room of a posh pub near his house in west London, dressed in black, with a swept-back white quiff and clunky clear Perspex glasses by the fashion brand Jacquemus. “I used to see Freddie in clubs but I was much too shy to approach him. Elton John once took me to dinner and George Michael was there, but we didn’t click. They were such megastars – I never felt in their league.”

For much of 1984, however, Johnson might have been bigger than all of them. Forty years before Brat summer, Frankie Goes to Hollywood, a Liverpudlian band comprised of three straight men known as “the Lads” and two flamboyantly homosexual frontmen (the other was the mustachioed dancer and backing vocalist Paul Rutherford), caused delighted outrage across Britain and beyond. Back then, the few out gay pop stars soft-pedalled their sexuality (Boy George famously told chatshow host Russell Harty that he preferred a cup of tea to sex), but Frankie went full throttle in the opposite direction, taking their look and attitude from the leather bars and bath houses of the gay demimonde, a blatantly sexual look that was as intimidating as it was thrilling.

“Tom of Finland was a huge influence,” Johnson says, referring to the artist who drew smiling bikers and sailors going at it hammer and tongs. “We were told about the ‘twilight world of the homosexual’, where everyone was supposed to be lonely and miserable, but he showed gay men in a different light – happy, fulfilled and having fun.”

This hedonistic ethos more than met its match in Frankie’s music: Relax had lyrics about delaying ejaculation, underlined by Johnson’s orgasmic growls and grunts of “Huh!” The producer Trevor Horn had blown their song up to epic proportions, turning a punk-funk chant into a throbbing floorfiller with the aggression of a rock classic and the sound effects (including copious squirting and splashing noises) of a George Lucas blockbuster. After a spectacular Top of the Pops performance in January 1984 (Johnson wore a yellow bandana in the back pocket of his leather trousers, which in the “hanky code” of the San Francisco gay underground denoted a sexual practice not often alluded to at 7pm on the BBC), Relax vaulted into the Top 10 before Radio 1 DJ Mike Read declared it obscene. It was then banned from broadcast by the BBC and shot to No 1 for five weeks.

Frankiemania was unleashed: Relax’s pulverising follow-up, Two Tribes, took the then prominent threat of nuclear annihilation as its subject and spent nine weeks at No 1, while Relax rose inexorably back up the charts over the summer, joining it at No 2. The band’s T-shirts, with slogans including “Frankie Say Arm the Unemployed” and “Frankie Say War! Hide Yourself” emblazoned chests nationwide – 250,000 official tops had sold by the end of the year, along with an estimated 500,000 pirated versions.

Frankie concluded their annus mirabilis with their third and final No 1, The Power of Love, which lasted a week at the top before being swept aside by Band Aid’s Do They Know It’s Christmas?. The song is now a festive classic and recently played a key role in All of Us Strangers, Andrew Haigh’s film about a gay man coming to terms with childhood bereavement and the homophobia ubiquitous in the 80s. “I sobbed my eyes out watching that film,” Johnson says. “And I was very surprised to see my younger self being watched by the main character.” This is depressed screenwriter Adam, played by Andrew Scott, watching an old Top of the Pops performance of The Power of Love late at night, when the younger Harry (played by Paul Mescal) comes to his door.

Johnson’s presence in the film seems to signal the promise of emotional fulfilment, of being gay and also being loved, and there is no doubt that many found his unapologetic queerness hugely inspiring at a time when gay people were so poorly treated – with no marriage or adoption rights, no protection against discrimination in the workplace, and an age of consent of 21 for gay sex, five years higher than for heterosexuals. “I still get messages saying: ‘I lived in a small town and you were a huge affirmation for me of my otherness and my sexuality,’” he says.

Such people – and plenty of others – will flock to an exhibition about Johnson’s life that opens this weekend at the Museum of Liverpool. Do the exhibits include his old rubber vests? “There is some fetish wear, but none that I actually wore, because rubber tends to disintegrate and leather knickers get lost along the way,” Johnson, 64, points out. Other exhibits include his paintings from the late 80s and 90s (something he’s always done alongside music); his Vivienne Westwood suit from the video to his 1989 solo hit Love Train; and a jacket made for him by the late performance artist Leigh Bowery, for a performance benefiting Aids charity the Terrence Higgins Trust. “He came to my house wearing a very strange old-lady wig and he was wearing stiletto heels inside big boots, so he appeared very, very tall,” Johnson remembers.

Such outre characters had shown the man born William Johnson that there was more to life than his repressive immediate surroundings. “That whole 70s bohemian, blurred sexuality – The Rocky Horror Show, The Naked Civil Servant by Quentin Crisp – all those things were clues to a world that was far removed from being a working-class lad in Liverpool,” he says. He became an ardent fan of David Bowie and felt inspired by Andy Warhol’s entourage of gay and trans superstars, taking his first name from one of them, Holly Woodlawn, who Lou Reed immortalised in Walk on the Wild Side (“Holly came from Miami, FLA / Hitchhiked her way across the USA”). Johnson met her years later and she was flattered that he’d borrowed her name. “She was fabulous! It was so nice to meet her after seeing her in Trash with Joe Dallesandro when I was 14.”

Johnson’s experimentation with his identity – from shaving off his eyebrows to reading Jean Genet – put him on a collision course with his parents, a taxi driver and a nurse, who were sometimes so embarrassed by his appearance that they tried to stop him leaving the house. In his autobiography A Bone in My Flute, published in 1994, the singer describes his father, who had joined the navy at 14, flying off the handle when the teenage Holly was offered an alcoholic drink one Christmas and requested a Babycham. “‘No son of mine is going to drink fucking Babycham!’” Johnson laughs. “My dad thought I was a freak. He didn’t know any other children who dyed their hair and wore makeup to school.”

Johnson and his friend, nicknamed Honey Heath, became outcasts among their classmates. “He was tall, blond and Bowie-esque, so he stood out like a sore thumb,” the singer remembers. “We were battered and spat at every time we went into school. The abuse was physical and verbal and it was daily. So we played truant a lot. We went to St John’s Precinct, which was where we first saw Jayne Casey and Pete Burns, who were working in a hairdressing salon called A Cut Above the Rest.”

The aggressively androgynous Burns used to terrify Liverpudlians with his caustic wit and black contact lenses; he later became famous as frontman of Dead or Alive. Casey was locally notorious for having a shaved head and went on to sing with Pink Industry, before becoming a mainstay of Liverpool’s art scene. “It was fascinating to us that there were other freaks in the world who were out there working, having a job – albeit in a unisex hairdressers.”

This defiant self-expression came into its own when punk hit Liverpool. In 1976, Casey took Johnson, who had been writing songs from the age of 13, to the nightclub Eric’s, the centre of the city’s alternative music scene. The pair formed a band called Big in Japan with Budgie, Bill Drummond and Ian Broudie, all of whom became highly successful years later with Siouxsie and the Banshees, the KLF and the Lightning Seeds, respectively.

But Big in Japan weren’t big anywhere beyond Eric’s, and even Frankie Goes to Hollywood struggled after forming in 1980. “We’d done two Peel sessions and we were gigging around the north-west, but it looked like we weren’t going to get signed, even after The Tube.” They performed Relax on the Channel 4 pop show in the company of two lightly clad, whip-cracking female backing dancers called the Leatherpettes. “We were on the point of breaking up. I applied for art college and got in. I was supposed to go in September 1983 – but then Relax came out in October.”

Frankie had signed to Horn’s label ZTT, in what was a brilliant artistic decision but a terrible financial one. “Our deal was unimaginably bad,” Johnson says. They had an 8% UK royalty rate for album sales, about half that received by other bands in the same position; ZTT retained control of their producer, choice of studio and recording costs; they signed their publishing away to a company owned by Horn; and anyone who left the band had to remain contracted to the label regardless. However, “we were starving – I’d been on social security benefits for about seven years and the choice was, take the local education authority grant to go to art school or do the thing I’d been working on since I was a young teenager. Signing a bad deal meant nothing – I just wanted to make great records.”

Nonetheless, the extent to which they’d been exploited was not only apparent to the band – “when we saw the royalty statements and realised that we’d been taken for one big ride” – but by their pop music peers too. “Bronski Beat went around throwing scorn on us for signing that deal because they’d been offered it, but they had other options,” Johnson says. “Even when Neil Tennant interviewed me for Smash Hits” – a couple of years before he left the pop magazine for a new career as a Pet Shop Boy – “he was looking down his nose at me for signing that bad deal, but I didn’t give a toss, really. I made better records than all of them, as far as I’m concerned – records that have stood the test of time in a way that none of theirs have.”

ZTT felt few scruples about shafting Frankie, he adds. “Their attitude was that we were these five oiks from Liverpool that they’d moulded and created this huge success.” Johnson eventually had to take ZTT to court in order to sign to another record label and launch his solo career. After a hugely expensive two-year battle, ZTT lost, the judge saying that their contract “was not a fair deal”. Horn has since expressed regret, but this doesn’t cut much ice with Johnson. “His initials are TCH, and to me they’ll always stand for That Cunt Horn.”

Johnson felt vindicated by the fact that his debut solo album Blast went to No 1, while the singles Love Train and Americanos were top five hits. However, a follow-up album flopped, a situation Johnson was soon in no fit state to remedy. In October 1991, after suffering skin lesions and a fungal infection on his toenails, he received a life-changing medical diagnosis.

“I’d presented with enough symptoms for it to be classed as Aids, rather than just being HIV-positive,” he says. “There were certain criteria, which was a very low CD4 blood count” – the white blood cells that attack infection – “and an Aids-defining condition, which for me was Kaposi’s sarcoma, which is a cancer of the blood vessels in the skin. You would see photographs in the media of very thin men with disfiguring purple blotches and that was all part of the fear that surrounded HIV infection.”

Johnson developed Kaposi’s lesions on his arms, chest and face, which were treated with radiotherapy; the 31-year-old was told that he had between two months and two years to live. “Close friends and flatmates died around the same time I was diagnosed and I was convinced I was next.”

In the spring of 1993, he bravely decided to tell the world about his illness via an interview with the Times. “But it turned into a bit of a debacle because Piers Morgan” – then editing the pop pages of another Murdoch paper, the Sun – “stole the interview off the Times database and published excerpts from it in a very sensationalised way on the Thursday before the Saturday it was due to run, and my parents got doorstepped, which was very unpleasant.” Johnson was all too aware that many people at the time regarded Aids as just deserts for the kind of gay hedonism he’d exemplified. “It felt like being cancelled,” he says. “For quite a number of years no one rang except a couple of friends like [Radio 1 DJ] Janice Long and Kirsty MacColl.” The singer used one of his paintings on the sleeve of her single Angel.

There was another notable exception. “I got a phone call from David Bowie, which was like getting a phone call from God. We ended up chatting for over an hour on a Saturday night. We spoke a lot about art – the Vorticists and Keith Vaughan – and he said, ‘I’ve got a tour coming up; what songs shall I sing?’ So I just reeled off a load of songs that I loved.”

Johnson suffered not just from his illness, but from the medical treatment. “You’d grab experimental drugs with both hands and one of those gave me pancreatitis for five years, which is a very painful condition.” He did, however, become closer to his father. “We bonded over ill health – he had angina and gout. I remember when he rang me up after hearing about combination therapy on the news and said, ‘I was glad to hear there’s hope for you.’ So yes, we came to terms with each other.” Johnson’s father died in 2001; his mother is 89 and he still visits her regularly in Liverpool.

Combination therapies turned Aids from a terminal condition into a manageable one, saving Johnson’s life and those of countless others. As he puts it: “It is due to the miracles of modern science I’m still here and working.” Next June, he is set to mark the 40th anniversary of Frankie’s debut album, Welcome to the Pleasuredome, with a six-date tour in venues including the Royal Albert Hall in London and the Liverpool Arena. “I’m very aware that people buy tickets to hear the hits,” he says. “My value as a performer is very much in the songs. They somehow protect me and that’s why I’m a headliner at festivals, because of the songs and my ability to sing them.”

Will Frankie Goes to Hollywood ever reform? Last year, they played together for the first time since 1987 to celebrate Liverpool hosting the Eurovision song contest; the set consisted of a single song stipulated by the organisers, Welcome to the Pleasuredome. “I’m amazed it came together,” Johnson says. “There was a ridiculous amount of correspondence in the two weeks coming up to the event. But once we were there and we’d done the job, it was absolutely fine. I had a drink with them afterwards at the Bridewell, where we used to rehearse, which is now a bar. It was pleasant to see them and pleasant to leave them.” So don’t hold your breath for an Oasis-style reunion (about which Johnson, for the record, says: “I don’t give a toss”). “Fans ask me about us reforming on social media but I’ve given up replying – it just seems so unlikely.”

• Holly Johnson’s Welcome to the Pleasuredome 40th Anniversary Tour starts on 6 June 2025 in Birmingham and tickets are on sale now. The Holly Johnson Story exhibition at Museum of Liverpool opens 14 September and runs until 25 July. Details at hollyjohnson.com