UK pop star goes undercover to prank The Voice coaches

British singer Jess Glynne - pictured on stage in Berlin, Germany earlier this year - pranked the celebrity coaches on The Voice, by taking part in a blind audition on the show. Photo / Getty Images

A Grammy award-winning British singer has gone undercover to audition on The Voice in a bizarre prank on the four celebrity coaches.

Jess Glynne, who was the opening act for the Spice Girls' much-hyped reunion tour, performed her own song I'll Be There for Boy George, Delta Goodrem, Kelly Rowland and Guy Sebastian during Monday night's episode.

While the stars had their backs to the 29-year-old singer, the audience could see who it was and jumped to their feet.

Luckily, all four judges turned their chairs very early in the song and were quickly up and dancing as they realised who the mystery performer was.

"I have to ask … Hello, what's your name and where are you from?" George joked.

"I'm Jess!" Glynne replied, before admitting she was feeling nervous up on the stage.

"You know what, when you're all sat there, it's mad scary. Whoever does this, I'm really proud. Big up."

Sebastian had a big fan moment with the star, telling her he uses her as "an example" to his contestants.

"When you're on the radio, you sound like nobody else. I love your voice," he gushed.

Glynne wasn't the only familiar face to pop up during last night's episode of The Voice.

Nathan Foley — a former children's entertainer who was part of the original Hi-5 line-up — performed Footloose, turning Goodrem and George's chairs in the process.

Both Goodrem and Sebastian recognised Foley from Hi-5, with the Australian Idol winner gutted he didn't turn his chair.

"It's funny because singers in this country always knew that Nathan, like, is a beast singer. And I am kicking myself for not turning, I really am," Sebastian said.