'I'm not a celebrity person'

Given her brand of attitude-heavy punky pop, the Hertfordshire-born 22-year-old is a perfect fit for Perry. And Charli's enjoying herself, too.

"Well we're here in Bratislava, Slovakia, and the tour's been great so far. I've not been out, I've been doing interviews, so I haven't seen anything on this tour, as per usual, but the arena is wonderful."

She says her music has been going down well with Perry's crowds, though she admits she's more experienced now than when she supported Coldplay, somewhat less successfully, in 2012.

"I remember one night with them, I did this terrible performance and got loads of abuse online. And I reacted to all of it because I was being a little bitch. I had no idea what it was like to play in a stadium, I just played as if I was still in a club," she says.

"I'm getting better at that sort of thing now. I know how to win people over if things aren't going my way."

With songs like current single Doing It, her duet with Rita Ora, or Break The Rules, it's unlikely she has to work too hard to win the crowds over. Although she has noticed the latter song, with its chorus - "I don't wanna go to school, I just wanna break the rules, boys and girls across the world, putting on our dancing shoes, going to the discotheque, getting high and getting wrecked, I don't wanna go to school, I just wanna break the rules" - gets a mixed reaction.

"There are loads of kids screaming the words, and loads of parents looking like they hate me," she says. "But that's as it should be, it's always good if parents hate you."

Charli was born Charlotte Emma Aitchison in Stevenage in 1992, and grew up in nearby Bishop's Stortford, attending the famous school of the same name.

She started writing songs aged 14 - and soon after that, started being written about in the national press.

But despite the media buzz, by 2010 she was already taking a break from music, during what she has described as a "lost period".

In 2011, she appeared on MTV's Brand New For 2012, the TV station's annual list of artists to watch out for in the coming year, but while fellow nominee Lana Del Rey went on to global fame, things just didn't really happen for Charli. Publicly, at least.

Behind the scenes, she was writing for other artists, most notably Icona Pop's number one single I Love It.

She's reluctant to paint her career path as a struggle, however.

"I've been doing other things," she says, icily. "I'm not a celebrity person, although now is the first time people are starting to see me in that light, weirdly."

She's speaking two days after the Brit Awards, and photographs of Charli have been in most tabloids, showing her emerging from an aftershow party looking 'tired and emotional' (as has become their euphemism for 'totally plastered').

"I've been busy, and I'm not constantly trying to make songs for the radio," she adds. "Obviously my label would want me to be on the radio all the time, but that's not my personal goal."

She says she always wanted to make pop music - but on her terms.

"If people like it then great, but if they don't, then whatever, it doesn't bother me. I've made a living from writing for people, if I want to get boring about it. So no, it's not been a long, tough road, but it is nice people are more into my stuff now, on more a mass level."

Despite playing to arenas and stadiums with other artists, she says she still loves playing small, dirty venues on her own.

"Obviously, I daydream about what I would do if I was headlining those stadiums on my own, but I prefer the smaller rooms," she says, adding that she doesn't get much satisfaction from songs she's written for others topping the charts, just as Fancy, which she helped write for Iggy Azalea, did in the US last year.

"A sold-out crowd is better than a number one," she says. "But being in the studio is better than all of that. Obviously, getting a number in the charts is a nice thing, but the cherry on the cake, rather than the main cake. It's not something I think about or aim for, or that you even can aim for. The main thing is that I like the music, and that's why I make it."

Her own album Sucker, her third, and second while signed to a major label, was released a few months ago. Charli says she thinks it's a great album - and many critics agreed - although she's already moved on to what she wants to do next.

"I've been living those songs so much longer than anyone else, so it feels a bit old to me and I'm glad it's out. It was finished in October, but the songs were done ages before that. Boom Clap and Gold Coins were written in May 2013. Thankfully, playing them live gives it all a new lease of life."

To make Sucker, she worked with the likes of Ariel Rechtshaid, Rivers Cuomo of Weezer, and Rostam Batmanglij of Vampire Weekend.

"It was all very natural finding them," she explains. "Ariel, I worked with on my very first singles and have known a long time, Rostam I met at South By South West in Texas, and Rivers, I contacted on Twitter because I noticed he was following me.

"I want to do things my way. I've always been very stubborn, and it's always been a fight.

"As a pop artist on a major label, it isn't always the most creative environment, but there are people who were there when I was really young, and are really fighting for my ideas.

"They respect me and let me do my thing, and that's really rare and awesome. If I wasn't in that position I wouldn't be doing this," Charli continues. "There's no point if it's not coming from me."

EXTRA TIME - TEAM CHARLI XCX

:: Ariel Rechtshaid: produced Charli's early singles and second album True Romance. Also works with HAIM.

:: Rivers Cuomo: Frontman of US rock band Weezer, he co-wrote Hanging Around with Charli. Also a huge football fan who supports Sheffield Wednesday.

:: Rostam Batmanglij: Vampire Weekend's multi-instrumentalist, he co-wrote two songs on Sucker. Also the brother of indie film-maker Zal Batmanglij.

:: Patrik Berger: co-wrote and produced several tracks on Sucker. The Swedish songwriter has also worked with Robyn, Lana Del Rey and Icona Pop.

:: Mr Rogers: Australian songwriter Jarrad Rogers, co-wrote and produced Doing It for Sucker, which features Rita Ora.

:: Sucker by Charli XCX is out now. She begins a tour on March 24. Visit www.charlixcxmusic.com