In March 2018, a week before flying out for their South American tour, Royal Blood went to see themselves in concert.
Or rather, the duo had seen a flyer for a Royal Blood cover band, who were playing down the road at Brighton's now-defunct The Haunt. "Why not check them out?", they thought.
"It was very surreal," says frontman Mike Kerr, "but it was also an interesting experience because I guess that's the closest we can really come to knowing what it's like to watch a Royal Blood gig."
He was impressed with what he saw: "The idea of a cover band is bizarre, but they're really good." But the show also gave him a unexpected perspective on Royal Blood's music.
"I took inspiration from it because I realised there were all these styles and atmospheres and moments in our set that were missing," says Kerr.
"If there's anything that inspires my songwriting it's the idea of a setlist, and our new album, I feel, fills a lot of those voids that were in our set before."
Royal Monster, the tribute band, only recently found out how they'd inspired the band who inspired them.
"My jaw dropped," says frontman Dean Whale. "We were a bit lost for words."
"Frankly, the fact that he said he understood what direction he wanted to take after seeing our show is bizarre - but it's excellent all the same," says drummer Rob Dowsett.
"Yeah, it's an honour, really," adds Whale. "Do we get royalties?"
Two years later, thanks to a lockdown-enforced delay, the album is finally ready.
Called Typhoons, it doesn't exactly reinvent Royal Blood's wheel: they're still powered by the kinetic union of Kerr's riffs and Ben Thatcher's thunderous drumming. But this time around they've added rich new textures, from disco string stabs and filtered-down synth to the surprising appearance of a piano ballad.
Kerr says the new sound is all about breaking self-imposed constraints.
"The way we've made records before was so limited. That was intentional, but it was also starving ourselves of these colours and these textures. When we finally made the decision to go forward and do it it was really fulfilling."
To expand their sound, the duo invited in their love of 70s glam rock and cheesy disco: "We're obsessed with the drum sound on those old Boney M records." They also drew on the French house sounds of Daft Punk and Justice.
If that puts off the purists, they couldn't be happier.
"Being in a rock band there can be this restriction on quality, based on making sure it's not too poppy or catchy. We totally got over that idea," says Kerr.
"To us that's preposterous and restrictive. I've always loved that Freddie Mercury idea of extravagant songs. We weren't afraid of this sounding good or catchy."
But behind those technicolour grooves, Kerr's lyrics have taken on a darker hue.
"I let my demons take hold and choke on me," he sings on the ominous Trouble's Coming. Other songs see him confronting "evil in my head" and "thoughts becoming parasites".
"Wake up every morning almost surprised I survived," he concludes on Limbo. "Blood on the pillow/Tears in my eyes/Slept in a murder scene last night."
The words reflect the physical and psychological toll of Royal Blood's stratospheric ascent.
"There were mornings where I woke up and I felt exactly that way," says Kerr. "I am surprised I'm alive. I did go absolutely mental for about seven years."
Royal Blood were only formed in January 2013, but they went from playing pubs to international success in just 18 months.
Championed by the Arctic Monkeys, who invited them to open their huge Finsbury Park shows, the band's debut album went straight to number one in 2014, selling 66,000 copies in a week. The following year, they were named best group at the Brits, with the trophy presented by their hero, Led Zeppelin guitarist Jimmy Page.
By the time of their second album, 2017's How Did We Get So Dark, the band were selling out arenas and touring with Queens Of The Stone Age. But the touring lifestyle did them no favours. Kerr was drinking every day and becoming increasingly unreliable.
"It just escalated," he says. "It wasn't all dark from the beginning. I just picked up this lifestyle that didn't suit me and it began to get the better of me.
"It got to the point where I essentially just tapped out and became incredibly destructive."
'Bored of myself'
His behaviour started to affect the band and his personal life.
"There seems to be romance around being in a dark place and being creative, but that's a load of rubbish," he says. "To be honest, I felt very uninspired. It made my lyrical content quite boring."
Giving up wasn't easy. "It was almost like the toy that was being snatched out of my hands, and I was gripping onto it," he says. But things finally came to a head on a trip to (where else?) Las Vegas. After ordering an espresso martini, Kerr spontaneously decided it would be his last ever drink.
"I could hear myself talking about the same old thing: 'One day I'll get sober and sort everything out,'" Kerr says.
"I was bored of my own conversation. So I was like, 'I've got to take control of this thing.' And it was the best decision I ever made. We wouldn't have this album if I hadn't done that."
He's now two years sober, and says the clarity has "allowed me to be a lot more vulnerable and more articulate about how I'm feeling".
It also gave the band confidence to embrace those house and disco influences - although Kerr says moments like the sweeping electronic synths that close Limbo have always been a hidden part of their sound.
"That whole filter down thing is actually something I always do in the studio, where if I'm writing lyrics, I want to pretend the song is playing next door. Then I imagine I can kind of hear the mumble of the words and I write them down.
"But on that particular song, we did it and it sounded so cool that it we kept it."
Not every song cleaves to the new Royal Blood formula. Boilermaker, produced by Queens Of The Stone Age's Josh Homme, is a twisted mutant rock beast, while the closing track, All We Have Is Now, is a tender, optimistic ballad.
It nearly didn't make the cut, until bandmate Ben Thatcher persuaded Kerr it deserved a place.
"I think it's a really special moment," says the drummer. "I thought it was such a reflection of what Mike can do in his songwriting, and it's something that we have never hinted at with Royal Blood at all. And so, if we're going to put out everything creatively that we enjoy, why shouldn't it go on the record?"
And that seems to be the band's new mantra: "We're not afraid of breaking the rules that we made."
"I feel like this album has given us a future, really," says Kerr.
"It's funny - usually at the end of making an album, there's a feeling of, 'Urgh, I never want to hear that again,' and the idea of writing other songs seems painful. Whereas this one didn't leave that taste in our mouths. I felt inspired to carry on."
But crucially, how will Royal Monster play it live?
"The thing is, we hear the songs when they're released, but we have to wait to see how we perform those songs live before we start working on them - because their live sound is quite a lot different," says Dean Whale.
"We've got tickets to see them play in August, so we'll have to wait a bit... but I think we're gonna be OK."