She can’t help herself, Charlotte Aitchison, better known as the musician Charli XCX – she’s obsessed with cars. Not in a Top Gear-quoting, ooh-what’s-under-the-hood kind of way: she couldn’t care less how many miles you get out of your Polo. Aitchison is more taken with the kind of car that comes with a driver and has enough space in the back for a sizable social gathering. Over a productive, decade-long career, in which this 25-year-old has turned out hours of thrilling and influential party music, she has always used cars as motifs for fun and for escape. I think of the “beemers” and “limousine-ers” in 2017’s brilliant earworm Dreamer, or the Porsches and passenger-seats that worked as lyrical fodder in this year’s bracing mixtape Pop 2.

The car, to Aitchison, is a creative space. We’re sitting in a brasserie near her record label’s offices in west London and she’s telling me about her mum and dad driving her down here this morning from their home in Hertfordshire, Aitchison silent in the back of their family wagon, gazing out of the window with her headphones in, listening to her own music on repeat – a series of new singles that she’ll release through the summer.

“I just like my own music,” she explains.

High-heel-tall in “Matrix style” leather boots, fronds of dark hair, she is dressed in a cream-coloured Helmut Lang shirt. It’s baggy enough that her father, Jon, this morning got confused. “He was like: ‘Is that my shirt?’ And I was like: ‘Daaaad, it’s fashion.’” In company she is self-assured enough to be a little remote, though at the same time she’s funny and thought-provoking. She doesn’t prevaricate. Still less does she apologise for who she is – either having made a policy decision not to shy from the fact of her genteel Hertfordshire background and her public school education, or (rare for a British musician with such origins) never thinking to be ashamed of any of this in the first place.

Charli XCX supporting Taylor Swift at Wembley, June 2018. Photograph: David Fisher/Rex/Shutterstock

She orders a grapefruit and a crumpet and eyes her phone for messages, explaining, brusquely, just how much she has on at the moment. As well as dropping those new summer singles, she is bang in the middle of the world’s biggest world tour. For weeks she’s been on the road with Taylor Swift, opening for the American megastar in stadiums and arenas on multiple continents. “I’m a really good performer so I can kind of get any crowd going,” Aitchison says, before acknowledging that at these giant Taylor shows it’s the mainstream-bothering version of Charli XCX who takes to the stage. “I play, like, the hits.”

Because there’s always been another side to this musician: the unbendable, ahead-of-her time pop-experimenter that the New York Times once referred to as a “Lady Gaga preamble”. It’s the avant garde, less accessible version of Charli XCX who will take to the stage a few hours after our breakfast, at a smaller, sweatier solo show in east London. “That’s where my music really goes down best,” she says. “The Taylor shows have been really great, but it’s a different beast… I’m not a pristine pop performer. I’m born to play in club environments, rave environments.” That, after all, was where it all started for her.

A decade ago Aitchison was in the back of the family car, another journey with her parents, this time looking for a place to park in Hackney Wick. She was 15 at the time, a precocious music-industry hopeful who’d got as far as branding herself (“Charli XCX” was a name she used in internet chatrooms) and even recording a dad-funded album of juvenilia (she later paid him back). She hadn’t gigged yet and this was to be her first show, at a warehouse rave.

My two friends from school, they work for me, they live with me… Every friend I have is a collaborator in some way

“I was told to be there at 10pm,” she remembers, picking up the story. “We got there at 9.30. The doors weren’t open yet. It was just me and my parents.” She thinks they waited there till midnight. And then she didn’t go on stage till 3am. Remember, she says, with a smirk, “I lived in Hertfordshire. I’d never been to a party like this before. I didn’t know anything about rave culture, or club-kid culture, or gay culture – everything was a first that night.” Aitchison’s head was turned, irreversibly. She wanted to be the kind of musician who could thrive at such parties – who could bring this kind of party to wherever she played.

I ask her whether her parents knew what they were opening their 15-year-old up to at the time. Aitchison, frowning, points out they stayed at the rave with her till 6am. So they can’t have been that uninterested. “My dad was very artistic and into music. When he was younger, he ran a concert venue for a while, so he was reliving his youth.” As for her mum, Shameera, Aitchison thinks she might have been “a bit nervous, yeah”. But then her mum had been through chaotic times in her teenage years that would make any rave appear tame…

Aitchison explains. Shameera grew up in Kampala in Uganda, part of an ethnically Indian family who were “kicked out of the country by Idi Amin… They were only allowed to take a certain amount of money with them, so they would roll up additional money and hide it inside toothpaste tubes. Mum remembers landing at Stansted and it was snowing. She’d never seen that before. She didn’t have a coat. They’d never needed coats in Uganda – they were freezing.” When I ask Aitchison what effect her mother’s story has had on her, she says, simply: “I find it inspiring.”

After that first, formative rave, Aitchison kept writing and performing, building up a sizable off-radar following for her live shows by the time she released her first studio album, True Romance, in 2013. That year brought mainstream success of sorts, though the circumstances of it were bizarre. I Love It, a demo that she’d decided not to include on the album, was picked up by the Swedish duo Icona Pop, and as an Icona Pop track (with Charli XCX as a featured singer, some of her demo vocals left in the mix) it went to No 1. A year later Aitchison had a sidecar-seat in another massive hit, a featured vocalist and co-writer of the Iggy Azalea song Fancy. “No 1 for seven weeks in the US,” she says, still amazed and impressed.

Watch Fancy here.

But there were wobbles in Aitchison’s career after these oblique successes. She started writing material not to please herself, she suggests, but instead to chase more chart-points. It all led to a bright, punky, slightly forced second album, Sucker, parts of which she says “feel fake” to her these days. “It was definitely a confusing experience, after Fancy, when things didn’t really go my way. I didn’t become, like, this huge big artist or whatever. That was definitely hard at points for sure.”

But the experience affirmed her original feelings about herself: that she belonged on the mischievous fringe of music, “not being told what to do, not wearing the thing that is going to look the most appealing in the music video, not smiling all the time in every fucking photo, [instead] creating my own language and my own world”.

The most visible upshot of this is that, since 2014, she has pretty well junked any traditional sense of record-releasing, never quite putting out another album-album and instead showering her fans in fits and starts with EPs, “mixtapes”, singles – including last year’s hit, Boys – always recording and releasing quickly before her interest wanes. “Especially in the last couple of years,” she says, “I just feel so unbothered by top 40 success.”

Charli XCX’s self-directed video for the 2017 single Boys.

As a general attitude it has freed her up to call people out when she wants to, even at the risk of career-damage. Last year she took to task the executives and managers she works with (“You have no idea how fucking hard it is to just release a free fucking mixtape in 2017,” she tweeted. “Everyone’s like, what about Spotify/Apple/upsetting other majors”). She was also the most brazen of the artists who criticised Neil Portnow, the president of the Grammys, who said in January that female artists should “step up” in 2018. Online, Aitchison threw back at Portnow a notion that she might just “step up” on his face for saying something so lazy. “Women are making amazing music right now,” she said at the time. “What the fuck is this dude talking about?”

Risk wouldn’t be risk, though, if you could flirt with it indefinitely without consequence. In May, Charli XCX was a featured vocalist on a Rita Ora track called Girls, which landed with a dreadful thud. It was felt the lyrics, partly written by men and telling of a same-sex relationship, made cliched and exploitative use of lesbian tropes. Aitchison winces when I bring the matter up. She was on tour when the upset first brewed and she wanted to give Ora, who is a friend, a chance to make public comment before she did. This meant an unaccountably long (for Aitchison) public silence, during which time, she says, she called friends in the LGBTQ community to get their takes. She apologised at the time for any offence caused, while also being careful not to throw Ora under the bus.

Any fan of Aitchison could see that the delicate approach wasn’t her natural mode. By June she was back to truer form, key collaborator on a wickedly barbed song called Bitches by an all-female cast including Tove Lo. On its release, Aitchison cheerfully explained to anyone who hadn’t caught on that the video was “all about teaching dudes to eat pussy right”.

“I feel like I’m in a space that only I could be in,” she tells me. “Nobody can do what I do, apart from me.”

These days she lives most of the year in Los Angeles, the city of cars, which makes sense. She gets to do plenty of Uber-ing around between her home and a studio, lost inside headphones, mute and plotting. “It’s one of my favourite places to be. It makes me happy,” she says. I start to ask, doesn’t that ever make you… “Lonely?” she says, finishing the thought, letting it hang there.

In trying to get a sense of her personal life in LA, it becomes clear she doesn’t really have one – not a life, anyway, that can be defined apart from its work. She says: “My two best friends I went to school with, they work for me, we live together. I like to keep business very friend- and family-orientated… I’m spinning plates all the time… I’ve always said I’m a workaholic, but I never actually knew what it meant, until I was Googling it the other day. And fucking hell.…” She recites the symptoms the search turned up: “That you don’t sleep well. That you swing between thinking of yourself as the absolute best in your field or the absolute worst, completely inadequate, a total piece of shit. That you turn every aspect of your life, people and places and fun, into work… Which is me. Like, every single thing is work for me. Every friend I have is a collaborator in some way.”

I ask how it made her feel, reading that description, and finding herself so accurately described. “Really sad. Because then it made me think, oh God, do I not…”

She pauses here: she sits back and turns her head. It’s the first and only time since she sat down that she’s seemed anything but ironclad-sure of herself. “Sorry. I feel like I’m going to cry if we go into it. But, yeah, maybe I need to not be doing that all the time. I don’t know. I feel like I don’t have anyone I can talk to about not-music stuff. Everything is music. You know?”

I suggest, cautiously, it might be healthy if she cultivated some relationships with people outside the industry. She growls a laugh and says, oh, she’s tried. Her first boyfriend was a film director.

And?

“And I made him direct all my music videos.”

She sits forward again, visibly shaking off the bluesy feelings. She says she’s got into funks before, and a gig has normally helped drag her out again. Luckily there’s that London show due in a few hours; later there’ll be glowing reviews in the papers and online. “Sometimes you might want to die, internally. But you deal with it and go on stage. When I’m on stage I’m never thinking, like, ‘I’m really sad’. I’m just releasing all my energy.”

Couldn’t she also write some of this out of her system too? Yeah, she says, she’s been thinking about that. “I feel quite alone at the moment, more so than I’ve ever felt in my life, and that will probably affect the [next lot of] music quite a lot.”

It’s an intriguing prospect, this writer of epic songs about epic parties, self-sure chronicler of after-parties and after-after-parties – starting to address tomorrow morning’s anticlimax. As she asks her listeners in one of the new summer songs: “Won’t you stick around for the comedown?”

Charli XCX’s latest tracks Focus and No Angel are out now on Atlantic Records. She is currently supporting Taylor Swift on her world tour