Demi Lovato has stated that it was an "honour" to perform with Jessie J.

The Brit played at the Triple Ho Show in California on Wednesday (December 3), with Lovato also on the bill.

However, she surprised onlookers by bringing out the US star for a rendition of her hit song 'Bang Bang'.

Lovato ran through Ariana Grande's lines as the crowd were sent into raptures.

Jessie J later said on Instagram to her collaborator: "Been wanting to sing with you forever! Tonight was special."

Lovato in turn said on Twitter: "That just happened.....Thank you SO much @JessieJ for having me on stage for Bang Bang...It was an honor!"

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Watch the duet take place below: