The singer was performing at Sandringham House in Norfolk when he introduced his “oldest friend from the band” and brought out Owen for a rendition of their 2008 single ‘Greatest Day’.
The pair embraced on-stage and lead a singalong from the crowd for portions of the track. “Mr Mark Owen, everybody,” Williams said after their performance, adding: “I love my boys.”
Watch fan-shot footage of the performance below.
The singer is also performing a second night at Sandringham Estate today (August 27), with the venue marking the final stop on his 2023 ‘XXV’ European tour, celebrating 25 years of his solo career.
Elsewhere, the singer recently made an unlikely appearance on Soft Play’s (formerly known as Slaves) new song ‘Punk’s Dead’.
Speaking to Jack Saunders on BBC Radio 1, Soft Play said that Williams was a fan of the band and wanted to collaborate in some way, which resulted in his surprise guest feature.
In other news from the singer, Williams recently said that he wants to recruit Radiohead for a cover of ‘It’s Raining Men’.
He told The Sun‘s ‘Bizarre’ column: “I want to do a cover of ‘It’s Raining Men’ but I want Radiohead to do a backing track for me.
“But they have not got back to me. I keep asking but nothing back. I dunno. I might ask Trent Reznor.”
Reviewing Williams at Madrid’s Mad Cool festival back in July, NME said that he was “still the ultimate showman”, who brought “melodrama and self-effacing humour to his back catalogue of hits”.
The four-star write-up added: “As he introduces ‘Angels’ by talking about how he overcame a decade of mental health issues, it is clear that, for Williams, entertaining thousands of people at festivals like this one still acts as a healing salve. He is a performer with more than enough heart to match his humour.”