Niall Horan had a special surprise up his sleeves during his Friday, August 23, concert in Dublin — a duet with Ed Sheeran.

“Can you please give it up for my good friend and the great Ed Sheeran,” Horan, 30, told concertgoers on Friday, per video footage shared via his social media pages. “Let’s have a bit of nostalgia [and play] a song that this man wrote.”

While the duet appeared to be a sweet moment between friends, fervent fans know it also put past bad blood in the rearview mirror.

Sheeran, 33, wrote One Direction’s “Little Things” with Fiona Bevan, who previously told Songwriting Magazine in 2019 that the true “50/50” collaboration stemmed from her initial idea. The Grammy nominee went on to write 1D’s songs “Moments,” “Over Again” and “18” as personal bonds with band members Horan, Harry Styles, Louis Tomlinson, Zayn Malik and Liam Payne deepened.

After years of post-1D friendship, Sheeran and Horan were caught in a love triangle, now a decade ago, with fellow singer Ellie Goulding that inspired an apparent revenge anthem.

Sheeran dated Goulding, now 37, first, once confirming that they were an item when they were seen holding hands at the 2013 MTV Music Video Awards. While it is unknown when they broke up, Sheeran’s “Don’t” the next year appeared to allege that Goulding cheated on him with Horan.

“I never saw him as a threat / Until you disappeared with him to have sex, of course,” Sheeran sings. “It’s not like we were both on tour / We were staying on the same f–king hotel floor / And I wasn’t looking for a promise or commitment / But it was never just fun, and I thought you were different.”

Neither Sheeran nor Horan even publicly addressed the love triangle, but Goulding denied being unfaithful.

After a fan questioned her fidelity in a 2023 TikTok comment, she clapped back at the notion that she cheated on Sheeran with Horan.

“False,” she commented. “But also slay.”

All seems to be water under the bridge. After their “Little Things” duet on Friday, Horan and Sheeran then performed an acoustic rendition of Sheeran’s “Lego House.”

“Thank you @teddysphotos for coming out to play with me tonight in Dublin. Another great memory,” Horan captioned his Instagram post.

Sheeran, who wore Horan’s The Show Live on Tour merch, even joined the Irishman backstage for a special post-show celebration.

“Myself and Ed are here backstage and we’re gonna try to split the G,” Horan captioned a Saturday, August 24, Instagram video. “For those who don’t know what split the G is, basically, you have to take one to two gulps or so [of a pint of Guinness beer] and land this black-and-white line in the gap in the letter G [of the cup logo].”

Sheeran, who hails from England, thought he had a “pretty good” attempt.

“You’ve absolutely nailed it,” Horan gushed. “I got nowhere near it. He’s more Irish than us! He’s the most Irish non-Irish man I’ve ever met.”

Sheeran is now married to former school classmate Cherry Seaborn and they share two daughters, while Horan has been in a longtime relationship with Amelia Woolley. Goulding, meanwhile, shares a son with ex-husband Caspar Jopling.