Every pop star knows the protocol by now: drop a track out of nowhere, everyone rushes to listen to it, watch it go viral.

Katy Perry is going for a more traditional experience for her new single ‘Chained to the Rhythm’ though, in a sense, by restricting first listens to people who seek them out.

Because she can, Perry has had disco balls scattered throughout the world that double as players of the song, which passers-by can plug their headphones into.

The disco balls have already been discovered in San Francisco and chained up outside the Moulin Rouge in Paris.

London’s meanwhile was located in Leicester Square.

"It's like bringing back old Katy Perry vibes,” one listener there told the BBC, “back to the Teenage Dream times. I can't imagine how good it's going to sound live on tour."