Among a number of people backstage at London's Islington Assembly Rooms, it takes a moment to realise the slight-framed girl in the baggy sweatshirt is the focus of the evening's sold-out show. The clue is not the stack of albums Laura Mvula is signing, nor the commanding presence often reported for divas. No, the shimmery gold-painted fingers and shorn midnight-blue hair are the giveaways.

It suggests a certain level of artistry, as does her top 15 album in Ireland, an Ivor Novello award, and the accolade of being one of Britain’s Leading Ladies by the purveyor of middle England tastes, Marks & Spencer.

Away from her varied accolades, Mvula’s three years of fame have also been punctuated by mental-health issues and her divorce from Themba Mvula, whom she married when she was 23. Suffice to say her second album, The Dreaming Room, discusses more than the woes of living on a tour bus – particularly Show Me Love, a searingly honest account of the gaping soul-wound left by the dissolution of that relationship (sample lyrics: “I miss belonging to someone / I miss the kiss of another/ I miss the morning / I miss the waking up”).

“Show Me Love is the cornerstone of The Dreaming Room,” she says. “If I was ever struggling with anything, my mum told me to write it down and never to keep it static; she wanted me to do something active about it. Music has always been that vehicle for me, so Show Me Love is an important moment for that record.”

Dark moments
Still, think twice before filing The Dreaming Room alongside other break-up albums. It meanders around the orchestral jazz-pop chasm between Julie Feeney and Janelle Monaé, and there are only fleeting dark moments. It also houses empowering anthem Phenomenal Woman (complete with a visually striking video) and the hope-filled Let Me Fall. Along the way, she reintroduces the keytar as an instrument to be taken seriously. It's more complex, more idiosyncratic than Sing to the Moon, which is a reflection of her desire to prove herself as being more than her classical training.

“It gets me nervous, the way I’m written about and presented in the media,” she says, with her slight Brummie lilt. “It’s a nice story that I was a receptionist for an orchestra and now I write orchestral music, especially because I’m black. That’s cool, but I could tell there was an overemphasis on it which was going to make people think that was it, and that’s never it for me, in any part of my life. Even my hair is going to change colour, length and texture. The Dreaming Room was always going to be something completely different.”

Mvula was born into a musical family in the southern suburbs of Birmingham. It was natural for her to take up piano aged eight and to join her aunt’s a-cappella group aged 15. She studied composition at the Birmingham Conservatoire, where she met Themba, who encouraged her to write her own songs.

A six-album Sony deal later, she was whisked into the studio for Sing to the Moon. With sleeper singles such as Green Garden and She, it was odds-on favourite to win the Mercury Music Prize in 2013 and would have done the job were it not for that pesky James Blake. With a little hindsight, was her debut as acknowledged as she wanted?

“Definitely not,” she says. “We should have won the Mercury, we should have won the female Brit Award too. I don’t think I should be recognised because I’m black, or because I’m a woman, but just because I’m killing.

“It’s very much the case that I’m likely to be one of those artists where I won’t be recognised until I’m dead and gone. It would be really nice to be celebrated in the mainstream and have chart success and all that, but really, a lot of talented people spend a lot of time figuring out why they haven’t. Sometimes there’s no justice, and that’s fine. The way I sleep soundly at night is knowing that it makes sense to me.”

Aware of how she might come across, she addresses her self-belief without prompting.

“When I first started talking, I didn’t say that for want of not coming across as arrogant,” she says. “If you’re a young woman in music and you say anything with confidence, you’re quickly labelled as a diva or aggressive. But I believe so much in this music, and that we don’t give enough platforms to all of the various forms and styles of music created. Contemporary music is so much broader than we present it to be.”

That might begin with the conservative nature of the industry, I suggest, but ultimately there is no accounting for people’s tastes.

“We’ve had it in western culture for a long time now, and it’s scary,” she says. “It’s the Donald Trump times of music. We’re like, ‘What? Is this a joke?’ But it’s true, it’s reality. The people at the top of the charts are great, and that’s their achievement, but we only shed light on specific things, and that in itself makes it boring for me.”

Current thinking, as suggested by the likes of Labour MP Chris Bryant (who drew James Blunt's insult "prejudiced wazzock" in return), blames the homogenisation of the arts on easier access for those with a privileged background. It's a point with which Mvula agrees.

“I get nervous when I find out there are arts cuts, because I know when I wanted to discover music intimately, if I couldn’t afford it, it would be covered by the government,” she says. “I owe so much of my creativity to this education.

“My ex-husband teaches as well as sings, and I remember we would often talk about his experience doing vocal lessons in private schools versus community schools. There was no lesser talent in either institution, but the mindset, what was made available to kids in private school and what’s expected of them is very different. And all of these details are key. If you make them feel like it’s not possible, it becomes a self- fulfilling prophecy.”

Panic attacks
With a clear mind and strong opinions, it's little surprise that Mvula has managed to stabilise her panic attacks and depression, which dogged her throughout the promo trail for Show Me Love. On the cusp of another round of intense touring, how does she keep up her mental strength?

“Every day, I try to remind myself of how far I’ve come,” she says. “I think it’s very easy to become overwhelmed by a present circumstance that’s negative or uncomfortable and go, ‘Well, shit, I may as well be on the floor because this just doesn’t feel good’. When actually, if I compare what I was like last week or last month, I see how far I’ve come. Like, I did a show here for my last album, and if you’d told me then this stage is going to be flickering with lights, that I’m going to be in a black catsuit with a keytar around me and my hair will be blue, I couldn’t have believed it – it was enough that I was standing in front of a microphone.”

With that, she excuses herself to change from baggy sweatshirt to figure-hugging catsuit, leaving no doubt at all about how far she has come and who is the star of this show.

• The Dreaming Room is out now