You think you know nerve-wracking? Think again. Adam Lambert sees your frazzled synapses and raises the stakes. In 2014, the former American Idol winner was invited to divert temporarily from his successful solo career to try out as the singer in Queen. Four years later, he’s made the role his own. At first, however, singing those legendary songs in front of Brian May and Roger Taylor reduced him to a puddle of anxiety.

“I was in awe,” says Lambert, speaking from his home in Los Angeles. “I couldn’t believe it was happening. It’s still surreal, but right at the beginning I was like, Are they really trusting me to do this? In rehearsals I was so searching for validation from Brian and Roger, to make sure they were approving of my choices and my approach. And they always were. They have always been so sweet and supportive.”

Few rock stars stamped their persona onto a band quite as definitively as Freddie Mercury. Nevertheless, since the singer died in November 1992, May and Taylor (bassist John Deacon retired some years ago) have kept the Queen flame – and name – alive in a variety of enterprising ways. Between 2004 and 2009, the bullish former Free vocalist Paul Rodgers led the line, but Lambert has proved an infinitely better fit. While remaining very much his own man, the 36-year-old possesses the requisite measure of flamboyance, style, wit, showmanship and soaring vocal prowess to do Mercury’s legacy justice.

It took a while, mind you. Lambert admits that he has grown into the role, while initially there were mutinous murmurings among the Queen faithful: Who was this reality show upstart daring to step into the shoes of a legend? Lambert knows all this, because he was unwise enough to search the internet to find out.

“Right at the beginning, the first thing I did, of course, was go online and look at the comments,” he laughs. “Even if something is considered a 100 per cent success, you look at comments on the internet and you’re going to be proved wrong! There were definitely some question marks – ‘What?! Who? What’s going on!’ – but I understood. It was new, and it took people a minute to get the idea wrapped around their head. But honestly, any sort of criticism that I noticed early on, I think it charged me to be better. I pushed myself. We’re at the point now where I don’t really see any of that criticism any more. We’ve won everybody over.”

The key to the project’s success has been ensuring that it transcends mere tribute or imitation. “Obviously Freddie was such an icon, and we make sure that his spirit stays with the show,” says Lambert. “Leaning on that legacy is beautiful, and an honour, but at the same time, it’s about making sure it feels current. A lot of that is down to just allowing the music to be in my body – after a while it becomes an instinct, very much like it is for Brian and Roger. It took me a little time to catch up, but after a couple of years on the road, you connect into a living, breathing unit. We’ve become a real team, and I’m very grateful that my ideas are heard. It didn’t have to be that way. If they had said, ‘No! You have to do it this way,’ I’d have said, ‘Yes, sirs! Whatever you say.’ But they’ve been really lovely.”

Lambert describes performing with Queen as “like climbing a big mountain. It’s daunting. I definitely have to do a little mental trickery with myself. The audience tends to be the thing that really pushes me up the mountain. They know every word to every song, it’s a dream to perform to people who are that connected to the material.” When Queen last performed in Glasgow, in December, Lambert recalls, “the audience was on fire, really loud and warm and interactive. The connection that those audiences have to the music of Queen is undeniable, and gives me such a lot. It’s charges my confidence and my ambition.”

Which are his favourite songs to perform? “It changes day to day, depending what mood I’m in. Somebody To Love is timeless, and I identify with those lyrics. I feel like I’m always searching for romance! Another One Bites The Dust is pretty therapeutic, for getting out any kind of aggression I might be feeling. Who Wants To Live Forever is a soaring, emotional nosedive. It feels super cathartic every night. Then there are songs that are silly and fun. I like getting goofy on stage with Brian and Roger. There’s a lot of playfulness there. There are so many genres and moods, the show kind of takes you everywhere.”

Lambert shot to prominence as the winner of American Idol in 2009, an achievement he recognises as a double-edged sword. “There’s a slight stigma with the reality TV show singer thing, especially within the industry,” he says. “There’s a bit of a raised eyebrow, to which I always say, ‘Look, it’s a hard business to break into, and I did what I needed to do to get my foot in the door.’ And I did. Here I am nine years later doing it, so why do you care? It was a great launching pad. I would hope that when people listen to what I do, that all of that doesn’t really matter.”

From the start, Lambert stood apart from generic reality show fodder. At 27, he was fully formed: gay and out, proud of his identity and unwilling to temper it to gain mainstream acceptance. Since then, he has become an outspoken activist for a range of LGBT issues.

“I try to approach these things by leading by example: not making apologies, being upfront and bold in my identity. Nine years ago, when I started, not a lot of my contemporaries were identifying like that. I had some great icons like Freddie, Elton John, Boy George and George Michael, but it was a different time. Some of them weren’t out at the height of their careers – so doing it in 2009 was a whole different ball game. Being queer and in the mainstream music industry has been an interesting journey. There’s definitely a balancing act between being an artist with personal integrity, and the business side of the industry. It’s not ever clear cut. There’s no handbook, it’s not black and white, which is tricky. I’ve had to read between the lines a little.”

He’s nonetheless optimistic that the industry is becoming better at accepting and reflecting a broader spectrum of sexual identities. “There has been so much progress made at striving to tell stories and connect audiences to all different types of identities,” he says. “I think the industry now realises it has a moral responsibility to connect to people, and there’s an audience out there for everyone. The top forty tends to homogenise things, but I can see it diversifying. The audience is telling the industry what they want, which is exciting, and educating people greatly. It’s a good time.”

Lambert’s last album, The Original High, was released in 2015. In between gaps in Queen’s touring schedule, he’s been working on the follow up. “I could have pumped out an album super quick, but I really want to get it a particular way. Time and perspective are my friends on this.” Performing with Queen has, he says, inevitably effected the new music he is making. “There is some creative crossover, for sure. I don’t think I’d go as far as to say that my new album sounds like a Queen album, it’s just that it has opened up my sensibilities. Some of the influences of that music and that era have influenced my own music.”

He is hoping the album will be finished later this year. However, the one thing we will never hear, he insists, is a new Queen album. “You media folk love that question!” he says. “In terms of the material, Queen is what happened with Freddie. That was the creation of these songs, and I don’t know if it makes sense to record anything new, it’s kind of not what we are. We’re a live performance collaboration rather than a writing collaboration.” One that, nerves be damned, has become super-skilled at conjuring up the kind of extravagant, thrilling and slightly preposterous spectacle the Queen legacy demands.

Queen + Adam Lambert play TRNSMT in Glasgow this Friday