The pop star Anne-Marie has squirrelled herself away in an alcove, in a corner of a café in south London. It is the middle of February, and she has been working in a studio around the corner, on her second album, and now she’s picking at a veggie breakfast, though it’s three in the afternoon. Her formerly blonde, newly pale-pink hair lights her up like a beacon, but I have arrived a little early, and she looks so quiet and self-contained, so tucked into herself and thoughtful, that I have a strong urge to turn around and leave her to it. I had heard she was a talker, expected the gregarious character that is larger-than-life in her videos, but my first impressions are that perhaps she won’t be much of a talker at all.

Within two minutes of sitting down, I know this about the woman born Anne-Marie Rose Nicholson: the name of her nephew, where she lives, where she grew up, why she’s baffled that her Wikipedia says her dad is Irish (he’s from east London), the results of a DNA test she did to find out her ancestry and the fact that she wrote a whole album that she decided to scrap, because she realised that what she’d come up with was too “ratchet”. The idea was, she explains, that it would be a reversal of the wronged woman situation she had picked apart on her debut album, Speak Your Mind. She started writing about being the cheater, rather than the cheated-on. “I feel like in the first album, I had struggles, and I was trying to get through that by writing them down, and then when I came to write the second album, I was like, yeah, I feel fucking great. I feel great in myself, I feel confident, so the whole album was really…” She starts laughing. “It was too much! It was so horrible. I was like, I don’t care, I want to be different now, and then it wasn’t until I did a show somewhere and this dad came over to me and said, ‘I just want to say, I’m so happy that my daughter listens to you because you’re a really great [role model],’ and I was like…” She clicks her fingers and grins. “I’m not releasing that album!”

So, Anne-Marie is a talker, after all. She is three percent Irish, five percent Scottish, a little bit Scandinavian, and as for the rest, “I’m just Essex, basically,” she laughs.

Breakfast over, she talks and talks, and she is open and unfiltered. At one point I ask her if she ever feels the need to keep anything back for herself. “I haven’t thought about that,” she says, surprised it might be an option. “I think the reason I’ve been able to even carry on doing this career is because I am so honest and I want people to know who I am. That’s been a great thing for me, rather than, you know, acting like someone else.”

“The moment I started to write songs I was being myself’: Anne-Marie. Photograph: Hayley Louisa Brown/Atlantic Records

At the age of five, Anne-Marie went to a dance school, which sent her to auditions and for a while she had a part in Les Misérables in the West End. Then she switched focus and became a teenage international karate champion before going back to music, taking up songwriting, and ending up as one of Britain’s biggest pop stars. Speak Your Mind was the biggest debut album of 2018.

When we meet, she is a month shy of turning 29, and has just released the single Birthday, currently clocking 16m views on YouTube. It’s an arms-in-the-air, get-your-mates-on-the-dancefloor smash about celebration, even if you’re broke, feel sad and thoughts of your ex are hanging around like a pungent aftershave. Her everywoman candour and knock-you-down vocal range have combined into a formula that she has spun into pop gold.

She is working away at the new album, version two, with a confidence that had previously eluded her. She has struggled to write songs because of her self-doubt and, even now, when she’s in the studio with people she has written with before, “I almost feel like they don’t believe in me.” She is starting to realise that it’s self-sabotage – all imagined. “It’s actually me in my own brain.” She has suffered with anxiety for a long time, has always been a people-pleaser and admits she longs to be liked. “What I want to do in life is make people happy. Every day I wake up and say, ‘I’m going to make people smile.’” Along the way, she neglected to work out how to please herself.

Anne-Marie started working on her own music when she was a teenager. “I didn’t spend time downstairs with my family. It was: in my room, put the CDs on, film myself singing, get better at singing, do that bit again. I think the passion for that overcame the bad bits.”

In the spotlight: on stage with Rudimental. Photograph: Richard Isaac/REX/Shutterstock

Her first hint of the spotlight arrived in 2014, when Rudimental took her on tour as a vocalist, and she sang with the band for two years. When her own music started to pick up speed, she toured with her friend Ed Sheeran, and did vocals on Clean Bandit’s Rockabye, which became the Christmas No 1 in 2016. When her debut album took off, in 2018, she turned out snappy platinum hit after hit.

As she became more successful, her anxiety grew. “It got worse when I became an artist. I was like, ‘Great,’” she says, dryly. “It got overwhelming.” She describes how it manifested as “just, preventing things that were easy. Little things, like going into a room full of people, I wouldn’t be able to do that. I’d have to get people to go in first, so everyone would look at them, then I could go in second.”

It was an exhausting period, not just because of her workload. “I just thought I was a weirdo. I didn’t understand myself. Then I found out it was anxiety, and I felt better as soon as I said it, as other people could understand.”

Ed Sheeran gave me one piece of advice: ‘Call your parents every day’

She traces it back to having a tough time in her teens. “I think I really started to struggle when I was in Year 8 or 9, and that just came down to me being a prick, to be honest. I became a horrible teenager, the worst kid you can have as a parent.” Even now, she feels the need to keep apologising to her parents for how angry she was, and how much she took it out on them. “My nan passed away when I was 12 and I think that affected me really badly.” They had been close. “She held us all together.”

There was another catastrophe, a far more teenage one but a significant one, nonetheless. When she started secondary school, she’d been popular. “And I loved it! I was going out with all the boys, and one would come up to me and say, ‘I want to go out with you,’ and I’d be like, ‘All right, I’ll dump him and go out with you.’ It wasn’t until I was with someone for a long time…”

There’s a pause. “Yep. I cheated on him with another boy and that changed everything. From then, everyone hated me.” Her friends stopped speaking to her, overnight. It seems so insignificant now, she admits. “But at the time, it was massive. I never told my family anything about it, because it’s almost embarrassing that people don’t like you. I’d go home and pretend I’d had a good day.”

Flying high: with Ed Sheeran. Photograph: @annemarie

Sometimes girls would talk to her out of school, then at school they would blank her, which left her with long-standing trust issues. “Honestly, until I had hypnotherapy, I had struggled with everyone I’d met, even the people in the label. They’d be like, ‘We’re on your side, we want the best for you.’ I was like: ‘Fuck off, you don’t!’” It sounds as if she was bullied. “Well, do you know what? At one point I guess it was that. But I also think I was a really sensitive person. I find it hard saying that word, ‘bullying’, because in the end, I feel bad for the people I’m calling a bully.”

Anne-Marie is close to her family; she recently moved back to Essex from London, just to be nearer to them. When she’s away on tour, she calls her mum and dad all the time, a trick she picked up from Ed Sheeran. She asked him for the one crucial piece of advice that he’d give to someone new to the music industry. “He said, ‘Call your mum and dad every day.’” Otherwise, she explains, they only see what everyone else sees. “And you want them to know everything else.” Her dad is a builder and handyman, and her mum a teacher – they’ve been together since they were teenagers, which has given Anne-Marie an idealised view of love.

“I thought that was what everyone was like,” she laughs. “I thought the first person I was with, that’s my husband. It made me intense! So the boys were like, ‘Eurgh, get away, we just want to have fun!’” She always wanted to get married, but now she’s older, and has seen a few friends’ relationships break down, she’s not so sure. “It just opened my eyes. Now I’m completely the other side. I’m not bothered.”

That disappointment in a romantic ideal comes out again and again in her songs. “I felt like the moment I started to write songs, even if they were really shit, I was being myself, and that’s what I loved about songwriting.” But even when Speak Your Mind got as big as it did, she questioned her abilities. “When I first started writing, I couldn’t write, so I think I never grew out of that. It’s like when I lost weight, I never really grew out of thinking that I was still the chubby Anne-Marie, you know what I mean?”

Bright eyed: as a little girl. Photograph: @annemarie

She was 19 when she started feeling “chubby”, she says. “I just ate loads. It wasn’t until a year later and I saw one of my exes at a pub, and he was like: ‘You’re looking healthy’.” He made me look at myself, and then I went the complete opposite direction and had a problem with eating.” Now, she is much more sanguine, at least when it comes to her body. “I just decided, do you know what? I’m just going to see what my body is supposed to be, go to the gym, feel healthy and whatever the shape my body comes out, that’s just what I’m supposed to be.”

There was another change, too. After her career had taken off, she started to question why she never felt present, in the moment. “I just felt like I wasn’t actually here,” she says, trying to explain it. She was so unsettled by the sensation that she went online to see whether she might be having a breakdown. There was an interview she did in Australia, at 27, when she was told everything changes when you get to 28. “I’ve always felt I was 20,” she explains. “I felt I was growing up, but not actually growing up. Then when I became 28, I was like, oh shit, I’m 28!” She laughs. “I don’t know if it was what she said that made it go into my brain, or if it actually is a thing that when you’re 28, you change, but I was sitting in my living room one day, and I just cried my eyes out.”

At the beginning of April, I give Anne-Marie a call to see how she’s coping with lockdown: “I’m a bit of a germ freak anyway, so it’s heightened everything,” she says, from her bedroom at home. She tells me she’s been on tour or working for seven years, so this is the longest she has been in one place for ages. “I honestly have never been so close to my friends and family at this point. We started on Houseparty and we have a schedule of what we do every day. On Monday, we have bingo. On Tuesday, we have a DJ night, so one of us plays music. Wednesday is quiz night. Thursday is Fitness Thursdays. Friday is Teach-Me Friday. Then Saturday is Quarantine’s Got Talent. So we’ve got a whole schedule.”

As well as enjoying having more time to herself, she’s still feeling the benefits of the hypnotherapy she had. “After it, I thought, how the hell had I been making other people happy, when I wasn’t?” she says. She’s still a people-pleaser, but now she feels better about that, too. “I know how good it feels to feel good,” she explains, happy, for now, in the moment.

Anne-Marie’s single, Birthday, is out on Asylum/Major Toms