Halsey delighted fans on Wednesday as she brought Ellie Goulding on stage for a surprise duet of her hit Starry Eyed during her Back to Badlands tour.
The American singer, 31, whose real name is Ashley Nicolette Frangipane, wrapped a three-night run at London's O2 Academy Brixton, marking the end of the European leg of the tour.
And for her final night in the capital, the star saved Ellie's, 39, guest appearance for near the end of the show, sending the crowd into a frenzy.
Introducing Ellie, Halsey told fans: 'Part of this tour and part of what I've been doing here is going back 10 years to celebrate this album that we all love so much, but in the process, getting the opportunity to rediscover the artists and the friends who made that time possible.
'Whether it was because they championed me, they collaborated with me, or they just may be someone to look up to - and by god did I need someone to look up to.'
She continued: 'There's one person in particular that I'm so excited to have here tonight.'
The American singer, 31, wrapped a three-night run at London's O2 Academy Brixton, marking the end of the European leg of the tour, and saved Ellie's, 39, guest appearance for near the end of her final night in the capital (Ellie pictured ahead of the show)
'She is an absolute trailblazer in this industry, and she's someone that I'm so, so lucky to have right beside me as a peer. And I'm just a really, really big f*g fan. Brixton, will you please give it up for Ellie Goulding!'
The crowd erupted as Ellie, who is currently expecting her first child with boyfriend Beau Minniear, appeared on stage.
The singer embraced Halsey before the pair launched into Ellie's 2010 hit from her debut album, Lights.
For the performance, Ellie slipped into silk green shorts layered over black sheer tights.
Showcasing her blossoming bump, she added a pop of colour with a three-quarter red cropped jacket featuring bright blue detailing.
She completed the look with oversized Yves Saint Laurent black shades and gold statement earrings.
The duo looked in their element as they belted out the track to thousands of fans.
Ellie, who already shares a four-year-old son, Arthur, with her ex-husband, Caspar Jopling, revealed her pregnancy as she walked the red carpet at the Fashion Awards in early December.
Since her relationship with Beau went public in September 2025, the pair have holidayed together in Italy, where Beau shared online an intimate photograph of Ellie lying in an unmade hotel room bed.
He also appears in several raunchy scenes in Ellie's latest music video, Destiny.
It comes after reports that Ellie had split from her management team as she plans a musical comeback with her sixth studio album.
Ahead of the currently untitled record's release, Ellie, whose last album was 2023's Higher Than Heaven, is believed to have parted ways with TaP late last year in a major shake-up.
The hitmaker signed with the firm in 2018 as she joined their star-studded roster alongside fellow chart-toppers Dua Lipa and Lana Del Ray.
A source told The Sun: 'As she moves into the new year with a strong sense of clarity, she is focused on family first with her second child due in just a few weeks.'
'Ellie is an artist who is a proven hit machine and is one of the most important and unique voices that has come out of the UK.'
Meanwhile, a source told Daily Mail: 'TaP resigned from working with Ellie on December 9th. They are proud of all they achieved together, but after eight years felt it was in both sides' interests to part company.'
The Daily Mail contacted Ellie Goulding's representatives and TaP management for comment at the time.
Speaking about the upcoming album, Ellie told NYLON: 'It had always been the goal to start this album; I didn't know it was going to be a divorce album, but that's the way it started heading.'
The singer exchanged vows with Caspar, the Harvard-educated grandson of Conservative MP Michael Jopling, Baron Jopling, at Grade I listed York Minster in 2019.
'When I married my ex-husband, I thought it was for life. That will never go away,' she said. 'There are some songs that are necessary for me to acknowledge that time in my life and to be respectful of it.
'Then there were some songs that were extremely reactionary and sad that I felt were good to do in the moment, but don't serve me long-term.'