Based on a true story, Pride shows how gay rights campaigners from London raised thousands of pounds for miners in the Dulais Valley, after the NUM had spurned their support.
Despite initial scepticism on both sides, the characters break down preconceptions and strike an enduring friendship.
Starring Bill Nighy, Dominic West and Imelda Staunton, the movie played to critical acclaim at the Cannes Film Festival this summer.
But, according to writer Stephen Beresford, it's a tale which had almost been airbrushed out of collective gay history.
"It was in the early 1990s, during the second round of pit closures, when I first heard about it," he said.
"As a naÃ¯ve 21-year-old, I asked the question: Why should we support the miners? They don't support us.
"Someone took me aside and said: 'Let me tell you a little story'.
"I suppose the film's been in the making ever since."
The film opens with gay activist Mike Jackson at the Pride march in 1984, looking for a cause to support.
He persuades his friends that "The miners are hated by Thatcher, the police, and the tabloid pressâ€¦who does that remind you of?", adding "The only thing we have to worry about which they don't is Mary Whitehouse, and that's only a matter of time"
Indeed, in real life it wasn't long until The Sun turned its moral indignation on the unlikely alliance as they branded a joint fundraising concert 'Pits and Perverts'.
But Mike quickly discovers that, in the beginning at least, not all the miners are entirely comfortable with the solidarity offered by 'Lesbians and Gays Support Miners'.
Christine Powell was treasurer of The Neath and District Miners Support Group, and recalls the first time LGSM visited Wales.
"Well we were nervous, not about them, but about ourselves.  We didn't know anything about gay people, none of us had ever knowingly met one, and we were just desperate not to say or do anything which was going to offend them - especially after they'd been so kind and supportive to us.
"But from the first minute they had us in stitches, and we soon realised that we had far more things in common than there were which separated us.
"Before that I suppose we'd been quite prejudiced, through ignorance.
"One of the good things to come out of the strike was that it forced us to be less judgemental about things we didn't understand, and realise that there are friends everywhere if you're happy to accept them."
After its West End premiere, Pride has its Welsh release in Swansea on Thursday, and opens across the UK on 12 September.
A film telling the story of how the 1984-85 Miners Strike united two utterly disparate sections of society is receiving its West End premiere.