Thirty years ago Rob Halford led Judas Priest, and heavy metal itself, out of the Midlands and into the bigtime. He tells us where the sound – and the look – came from

Peering from the window at his management company's offices in north London, Rob Halford assesses the sunny spring day outside. "Hmm, very nice," he says in his West Midlands tones, at once dolorous, friendly and a little puzzled – the wonderful Zen-bemusement of the Brummie accent. "Very nice, but I'm not sure if spring is very heavy metal. I think winter is the most heavy metal time of year. You have storms, ice, stuff like that."

Halford should know what is and isn't heavy metal. He's the singer in Judas Priest, who were crucial to the genre's genesis, something underlined by this month's 30th-anniversary reissue of their definitive album, British Steel. A charming and drolly humorous man with a screaming four-octave air-raid siren of a voice, Halford is the perfect ambassador for both heavy metal and Judas Priest. Halford's story has included arguments over bullwhips with Marie Osmond backstage at Top of the Pops, and being a covertly homosexual frontman singing a song called Hell Bent for Leather; there have been on-stage motorcycle accidents and parallels with the film This Is Spinal Tap. And while doing all that, Judas Priest helped form one of our planet's most enduring and pervasive musical forms.

Judas Priest's visual style – the head-to-toe leather and studs – and churning, riff-laden rock have influenced bands from Van Halen to Metallica, to Slipknot and beyond. In the process, they've affected our wider cultural fabric. Priest and their spawn have ingrained heavy metal and its comic-heroic ritual into our language and dress. But while heavy metal has gone international, the British Steel album – the record that, more than any other, codified what we mean by "heavy metal" – had a profoundly local origin.

With Judas Priest, the Midlands and metal reinforce one another with a wonderful literal-mindedness. Halford's dad was employed at a Walsall metalworking company, making components for nuclear reactors. Guitarist Glenn Tipton not only shares his surname with a Midlands town but was also an apprentice at British Steel. Judas Priest are the sound of the blast furnaces that once studded the Midlands.

"When we were kids walking to school," says Halford, "we'd walk past these metal foundries and see the molten metal coming out of the big vats. We were literally breathing in the fumes from these metal works, breathing in metal before heavy metal had even been invented. I'd be in school trying to do English literature and the classroom would be shaking because of the machinery."

"We really did grow up in a labyrinth of heavy metal," says Tipton. "Huge foundries, big steam hammers. It also gave you a determination to get out." Music was the way chosen by the members of Judas Priest.

The band formed in 1969, gigging around the West Midlands as a quartet with original singer Al Atkins until 1973. That year, their fortunes changed, when Halford replaced Atkins, a change reinforced when guitarist KK Downing recruited Tipton to join him. It was a slow grind to success, though. They had released five albums – moving from blues rock to pure metal – before British Steel took them to No 4 in the UK album charts and the US top 40, and its three hit singles – Breaking the Law, United and Living After Midnight (which they later performed on Live Aid) – brought them to wider attention via Top of the Pops.

Even when they were international stars, though, Judas Priest were dragged into trouble. In 1985, two young Americans, James Vance and Raymond Belknap, spent an afternoon drinking, smoking dope and listening to Judas Priest. Belknap subsequently killed himself with a shotgun. Vance maimed himself, dying three years later. The pair, it was later claimed, had been prompted by a subliminal message urging "Do it!" hidden on the 1978 song Better By You, Better Than Me. The men's parents sued, though when the case finally came to court, in Reno, Nevada in 1990, it was dismissed. Halford later observed that for a rock band to insert subliminal messages urging suicide wasn't a sensible way to build a fanbase. Better, he suggested, to insert the command: "Buy more of our records."

Less troubling were the band's parallels to the fictional metal band Spinal Tap. "I loved it," says Halford of This Is Spinal Tap. "But I've always said you can only make satire out of greatness. Everything's relative to that film. I went to Elvis's grave. I've said 'Hello Cleveland' when I've been in Detroit and we've definitely got lost on the way from the dressing room to the stage. In fact, we once got lost on the way to the fucking tour. We got off a ferry and couldn't find the bus."

Spinal Tap planned a musical, Saucy Jack, based on the Jack the Ripper story. Judas Priest predated this with Ripper, their own song about murder by gas lamp. The tale of the Ripper has featured in grand guignol theatre and music hall, and Judas Priest seem to touch on this tradition. Massively populist, they sometimes seem like music hall rerouted through Marshall stacks. And, as with theatre, there have certainly been costume changes. In the late 1970s, Halford emerged with a new leather-man look. When Judas Priest started making regular appearances on Top of the Pops, Halford was boldly accessorised with biker cap and bullwhip.

"Priest on Top of the Pops was absolutely spectacular," says Halford. "Once we were on with the Osmonds. I had my whip with me and I'd heard Marie wasn't happy about that. So, I went to see her in her dressing room with her curlers in." Did he use the whip on the show? "Of course I did. I'm not going to have any Mormon telling me what I can and can't do with my whip. Us being on Top of the Pops was great for heavy metal. We were the first band to go out with that particular look. Once it was there on stage and was being photographed, it just shot around the world. It just looked right – it looked like the music sounded."

Despite the homoerotic overtones of Halford's new look, he kept his homo–sexuality under wraps, not coming out until 1998 – in the middle of the period from 1991-2003 during which Halford had left the band. Presumably, Judas Priest's origins – the macho world of metal combined with the macho Midlands – might not have been particularly welcoming toward Halford's sexuality?

"Absolutely not," he says. "I understood that it could have been destructive. People were fascinated, but what would the knock-on effect have been? As it turned out, when I came out of the closet I was away from Priest. Back in the 1980s, though, I think there could totally have been a backlash. You protect your interests, don't you? I was also thinking about the rest of the band."

But were there clues on British Steel? The scream of "You don't know what it's like" on the track Breaking the Law. Most particularly, some of the lyrics to Grinder: "Never straight and narrow … Been inclined to wander off the beaten path."

"It would have been subconscious," says Halford, "But quite possibly, yes. I think that's the first time I've ever been asked that question and, yes, subconsciously, maybe that's what it was. It certainly felt right. Why would I say 'Never straight and narrow'?"

And what about the leather? Was that also a signal? "It wasn't conscious. But how ironic that I chose that look – Glenn, the biker from the Village People. That wasn't my attachment, in terms of the gay community, but I understood the power of that look."

Alongside the biker togs Halford has used a Harley-Davidson motorbike as a stage prop, rolling out from the wings at the start of Hell Bent for Leather. During an August 1991 show in Toronto the bike collided with a drum riser that was hidden amid dry ice, breaking Halford's nose. He completed the gig before going to hospital. There was also a motorbike challenge to Freddie Mercury, issued live on Radio 1. Halford was supposedly outraged by Freddie's disgraceful employment of a static motorbike in Queen's video for the Crazy Little Thing Called Love single. He suggested a motorbike race.

"I never heard back from him," says Halford. "Freddie is my ultimate hero. The closest I ever got to Freddie was in a gay bar in Athens on the way to Mykonos. We kind of glared at each other across the bar, in a kind of smiling, winking way. When we got to Mykonos I was determined to track him down, but I couldn't because he'd rented this huge yacht. It was festooned in pink balloons and it just kept sailing around the island. He's someone I wish I'd really met."

Freddie, sadly, is no longer with us. But, as Queen once did, Judas Priest are still here to enshrine one of pop music's most important conjunctions – the place where the glorious collides head-on with the ridiculous. "Isn't it great?" he says with pride in his voice and a twinkle in his eye. "The blade is still as sharp as ever, 30 years later, still cutting through the metal world."

The 30th anniversary edition of British Steel is out now on Columbia