“Av you ever been up Greenwich Park?” he asked. I shook my head, conscious of every limb, then swiftly nodded. Yes, I’d love to go with him; our second date. He could have invited me to Chornobyl and I’d have agreed with celestial wonder in my eyes.

It was 1999. I was 17, he was 24, and he was about to become my first boyfriend. I already felt giddily, hopelessly, dangerously besotted. I knew we’d be an illegal couple – the age of consent wasn’t equalised until 2001. Frankly, I’d have served a decade in prison just for him to hold my hand, like he did in his off-white Vauxhall Nova on the drive there, breaking only to change gears.

First, he took me for strawberry cider in the Gloucester, a pub at the park’s edge, taking my trembling hand in his and reassuring me: “It’s actually a gay bar. We can be ourselves here.” I flushed with threat and relief, thrill and reluctance. Gay pubs are far more than bars; they’re refuges. This one, I’d learn, had a special significance. On Sunday, the first in a new series of rainbow plaques will be installed at the Gloucester – now the Greenwich Tavern – cementing its place in gay folklore.

Back home in the working-class Medway area of Kent, where we met when he sold me a phone credit card at the local petrol station, “queers” like us were widely perceived as predatory, perverted, suspicious or simply scum. It made me despise myself. Then, suddenly, this startlingly attractive, charming man was writing his number on the receipt. “I just got one too,” he said, pulling out his own brick-sized phone. “I should send you one of those ‘text messages’.”

After the strawberry cider, served by a man in a tight white vest – the only other gay man I’d seen in real life – the squiggly summer sunlight made a strobe effect through the park’s trees. He chased me through them, then pulled me in as the sun set between the ancient chestnuts. That single kiss transformed all the pain of the closet into the most beautiful thing I could imagine.

If I felt like I was in a film, it’s because I was: the seminal Beautiful Thing, written by Jonathan Harvey. Released three years earlier in 1996, after its 1993 run as a play, it is a story of forbidden same-sex teen love told on a Thamesmead council estate to the soundtrack of the Mamas and the Papas. The first time I saw it with him, when I was 18, I realised he had echoed the love story of the two protagonists, who also had their first kiss in the twilight of Greenwich Park’s trees, and their first experience of a gay pub at the Gloucester. He had watched it so often that the VHS tape flickered at the story’s key romantic moments. The explanation for his obsession is now clear: there was such a paucity of same-sex love stories that this was the first time many young people had seen a same-sex kiss, or peeked inside an actual gay bar after dark.

At the Gloucester, entertained by the mischievous drag queen Dave Lynn, the solidarity seemed especially magnetic. This weekend at the pub there will be a special screening of Beautiful Thing and a cast reunion. The project reminds people “that we have always been here, in good times and bad,” David Robson of the London LGBT+ Forums’ Network said when the plaques were announced.

This film and my own story were working-class gay love: not dandyish and sheltered by the politesse of privilege, but the brutal reality of being perceived a non-masculine boy. In claustrophobic, gossipy and traditional working-class estates, that left you vulnerable to humiliation, ostracisation and violence. It was a powerful and rarely told intersection – and one that, even more rarely, ends rather happily, with a beautiful scene of defiance and acceptance played to a Mama Cass waltz on the sink estate.

Later I discovered that I wasn’t the only wide-eyed baby gay my boyfriend had been chasing through those ancient chestnuts that summer. Upon finding out, I fell to the gutter next to the drains and cried till they felt clogged. But the film left me with a powerful feeling: that as long as there are places like the Gloucester, there are always joyously fun, safe sanctuaries for us to be ourselves when the outside world has left us sobbing. For me, the plaque honours that private moment as well as the shared history of the LGBTQ+ community.

That’s the message I’d impart to anyone who thinks such symbols are meaningless, as the unique social history of the UK’s gay bars is endangered by gentrification, hook-up apps, the cost of living crisis and even assimilation. As Robson says: “There are so many hidden LGBTQ+ histories at risk of being lost for ever.”

Just as I’m sure Jamie, the film’s protagonist, kept his mum’s Body Shop peppermint foot lotion (you’ll never view it the same way), I kept every tacky present my first boyfriend gave me. I wrote out by hand every text message he sent. The presents are long gone (I threw them in his face at the petrol station when I discovered the cheating). But the Greenwich Tavern remains ours. It’ll be poignant to walk in there again this Sunday to celebrate the unveiling.

Beautiful Thing was a saviour to me at a time of extreme fear and loneliness. To see someone of my class and sexual orientation was life-affirming. Like many working-class, closeted gay boys, I’d hide under the glovebox of my boyfriend’s Nova when we drove back from the park, lest anyone saw. Although he eventually broke my heart, the film stole and healed it. It whispered to cockney-accented gay boys like me: there are others like you. Find them. Canoodle among the ancient chestnuts again.

• Gary Nunn is an author and journalist