Even from the start, Fender knew the track had potential. Speaking to Genius, the 32-year-old said that he had “consistently liked this song” since he wrote it as a solo piece five years ago, and that the tale of regret and excess speaks to moments in his own life. Writing for Billboard U.K., Sophie Williams said that “Rein Me In” features “a vocal performance that delivers the type of passion and intensity that, the closer you listen, you can feel in your chest.”

Dean felt that, too. Both acts are signed to UMG U.K. labels, with Fender inked to Polydor and Dean on Capitol U.K. When Fender sent the album across to Dean, she picked “Rein Me In” as the song she wanted to contribute to and provided an original second verse, co-written with Max Wolfgang.

The mid-tempo rock song was flipped on its head, with Dean turning the original’s self-pitying diatribe into an open dialogue and offering a glimmer of redemption: “I see the tears of a man too proud to reach for a hand,” she sings, imploring to “let my love keep you safe now.” 

Richard O’Donovan, head of A&R at Polydor, tells Billboard U.K., “After the record-breaking launch of Sam’s People Watching, we could tell there was something special about ‘Rein Me In.’ We knew it had single potential, but we were utterly blown away when we received Olivia’s version. It brings a whole new lens to this incredible song.”

Fender’s 82,500-capacity show at the London Stadium was the Geordie star’s largest-ever headline show, and arrived after a number of U.K. indoor arena tours and festival headline slots.

Dean’s involvement, however, is something of a sliding-doors moment. Initially, The War on Drugs was set to be the main support for the show, an extension of Adam Granduciel’s production work on People Watching. When the group pulled out from the show, Dean was drafted in as a late replacement; “Nice to Each Other,” the lead single from her sophomore album The Art of Loving, was released the previous week.

Halfway through the show, Fender beckoned Dean to come on stage and revealed that they’d recorded a collaboration, and they were going to debut the song live together. “We’ll see how it goes,” he joked as Dean laughed with uncertainty. Two weeks later, the studio version of the collaboration was officially released on all streaming services. 

“Having these two extraordinary UK artists together on a track created so much fan excitement,” O’Donovan adds. “Once they performed it live at Sam’s summer stadium shows and everyone saw them together on stage, the live footage just exploded online and took the song to a new level. The same happened around Olivia’s recent shows when Sam surprised audiences in London – the response was phenomenal.”

Before Dean took over the U.K. Singles Chart with her solo material (“Man I Need” reached No. 1 in September 2025), “Rein Me In” hit No. 6 in late June after the revamped release. It would drop back and settle into a position in the mid-teens for the coming months before breaking inside the top 10 in November.

The song also exploited a quirk: Official Chart Company rules mandate that only an artist’s three most popular songs (based on combined sales and streams) can chart in the top 100 at any given time. The rule does not apply to features and collaborations, so “Rein Me In” allowed Dean a fourth entry into the charts, and capitalized on her growing stature. By October, Dean became the first female solo artist to simultaneously have four singles in the top 10. A month later, Fender released a concert film of the show on YouTube, further boosting the song’s popularity.

In late February, following Dean’s win at the Grammys for best new artist, the song completed a 35-week rise to the top spot, to give Fender his first No. 1 and Dean her second. The song went onto win the fan-voted song of the year at the 2026 BRIT Awards in Manchester just days later (March 1).

Only Harry Styles (“American Girls,” one week), Olivia Rodrigo (“Drop Dead,” one week; “The Cure,” one week) Ariana Grande (“Hate That I Made You Love Me,” one week) and Taylor Swift (‘I Knew It, I Knew You,” one week) have been able to dislodge the duo. Bruno Mars, Tame Impala, Alex Warren and Drake have all been denied a stay at the top spot during the reign of “Rein.”

The song has succeeded internationally, too. The song peaked at No. 64 on the Billboard Hot 100 to give Fender his first entry on the charts, and has topped charts in Ireland and Australia, alongside strong showings in the Netherlands and New Zealand.

During its 18-week stay at the summit, records have tumbled. The song dethroned Alex Warren to become the longest-running No. 1 of the 2020s (“Ordinary,” 13 weeks) and the longest-running No. 1 by a British act this century (Ed Sheeran’s “Shape of You,” 14 weeks). 

It passed Wet Wet Wet’s “Love Is All Around,” previously the longest-running No. 1 by a British act, after 16 weeks, and is now tied with just one song in the all-time ranking: “I Believe” by Frankie Laine (18 weeks, 1953).