Lewis Capaldi brought out surprise guest Sam Fender during his headline set at BST Hyde Park on 11 July, with the pair duetting on 'Rein Me In'. The moment drew a strong response from the crowd and on social media, and highlighted both the friendship between the two artists and the recent chart success of the track, which Capaldi noted had become "the longest-running British Number One single of all time".

The Scottish singer-songwriter topped the London bill with fan-favourites including 'Before You Go', 'Someone You Loved' and 'Bruises', before Fender joined him for 'Rein Me In' — originally a collaboration between Fender and Olivia Dean. The two officially released their version of the 'People Watching' track last summer after performing it live in London and Newcastle, and fans are now calling for an official Capaldi version. Capaldi has previously credited Fender and Fontaines D.C. frontman Grian Chatten — with whom he jokingly forms "The Syndicate" — for inspiring him to take more creative risks, and he returns to BST Hyde Park's Great Oak Stage for a second show on 12 July as part of his UK and Ireland tour.