Katy Perry

The Roar artist is one of the most successful female pop stars of the 21st century but still gets nerves about performing in front of big crowds and often feels sick at the prospect at doing so.

Speaking back in 2010, she said: "I was emotional before I sang Firework. I got chills and butterflies – it's a huge adrenaline rush. All the hairs stuck up on my body and sometimes I don't even have to sing because the crowds sing it louder.

"I still feel nervous performing to crowds. It's not that I don't feel ready but I worry that they'll rush the stage as they're all screaming my name."