The Crazy in Love beauty was belting out her hit Love On Top at the MEN Arena when she motioned to fans to sing along with her. She then picked out an excited McElderry, who was standing with friends right by the stage, to show off his vocals - and the hitmaker, seemingly unaware of his prior fame, was clearly impressed with his talent.
Dropping her jaw in surprise, she said, "You can really sing! You sound beautiful."
After the show, McElderry - who won Britain's The X Factor in 2009 - took to his Twitter.com page to express his glee at the 'duet', writing, "SO I HAVE ACTUALLY JUST SANG WITH BEYONCE (sic)!! she kept passing the mic back to me!!!!!! i can die a happy man now!!!!!!!"
It's not the first time Beyonce has chosen a famous face to sing during her U.K. tour - she previously invited British royal Princess Eugenie to sing a line of Irreplaceable with her while onstage in London, but the Queen's 23-year-old granddaughter was too shy to take the microphone.