Last November an almost offens­ively amazing new song appeared in the Popjustice inbox. It was called Someone New, it was by Astrid S, it was scheduled for a 2019 release and it was a Charli XCX and Noonie Bao cowrite. The track, a sparsely-produced envy anthem about an ex's new 'beau', must have leaked in one form or another at some point because lyrics were already on Genius, where the only annota­tion was this: "'Someone New' is an unre­leased Charli XCX song, allegedly sold to Astrid S."

Was this rather blunt summary true? Was this extraordin­ary jeal­ousy­banger really just grabbed off the shelf by Astrid S, in the same way the rest of us grab bleach and a Twix in Tesco? With Someone New finally released this week it's time to get Astrid S on the phone to find out.

When Astrid calls she's in Stockholm, where she's just been in the studio re-recording some vocals for a song whose key ended up changing. She's off to get some food in a bit: “Probably some soup.” You don’t think of popstars eating soup, do you? What a world.

Someone New started to take shape, from Astrid's point of view, at the start of 2018. "It was actually the first song I made by emailing," she says. Everyone has been doing emails! "I’d written with Noonie before, and I'd worked with the producers [Jack & Coke] before, but Charli XCX was part of writing and I’d never met her yet. So we were just emailing about it."

The song was partially formed when Astrid heard a rough, she says, "then I jumped on it, and we started writing. The bass was already there — it was a rough demo with some of the melodies. Then we just started working out the bits and pieces and lyrics and everything. Then I went to the studio in Stockholm. It was kind of messy, but it went smoothly as well."

We talk a bit about whether there was a point while the song was coming together when any of the other con­trib­ut­ors suddenly went: "Hold on, this has turned out to be extremely excellent and I want to keep it for myself."

Charli never said anything so I guess she was alright with it being my song," Astrid smiles. (Does she smile? Who knows, we're doing the interview on the phone. Seems like a smiley kind of statement?) "I do wonder about that myself, though," she adds. "I wonder what it’s like when you write for someone else and maybe you want the song yourself. Is it a no-go?"

Lyrically, Astrid says she wanted the song to be "more on the surface and super-simple" compared with previous songs like Emotion and Closer, which she considers "very meta­phor­ical". "You feel haunted if you think about someone a lot," she says, "and the song's about the feeling of being a bit obsessed over your ex meeting something new, and then you start stalking them." As Astrid notes, these days the stalking's often done on your behalf. "Because of algorithms, people will still appear on your phone — you’ll see them every­where."

Regarding the line in the song about talking like a psy­cho­path, Astrid says this: "I've felt a bit creepy in the past. When I’ve been in a situation where I'm obsessing over an ex, and I get these crazy thoughts.” ABOUT KILLING THEM? “No! Not killing them. Everyone goes through that obsession with an ex. In the moment you can feel, like: ‘Oh my god, I’m a psy­cho­path.’”

For the avoidance of doubt: Astrid S, are you a psy­cho­path? "I know I’m not a psy­cho­path.”

Astrid's ambitions for Someone New are fairly standard — she hopes her fans like it, she hopes it helps her find her way to other countries and so on — and she's planning a couple more singles before an album. There's been a lot of work done in London, as well as with producers like previous col­lab­or­at­ors Wolf Cousins (the outfit's Oscar Holter and Rickard Göransson worked on Breathe, for instance) and The Monsters & Strangerz. “I’m trying to be as quick as I can to finish the music, while also trying not to stress about it," she says. Which seems like a sensible way to be approach­ing things.