In addition to penning hits for the likes of Chris Brown, Miley Cyrus and Alicia Keys, vocalist/songwriter Jessie J's glittering pop hooks have brought her to the top of the UK charts and the coaching panel of The Voice UK. James Bay supports.
We've got some good news. Whether you missed out on tickets or went along and wanna relive the night, you can watch this performance live or on-demand.
Check it out on iPhone, iPad or iPod touch, iTunes on your computer or in stunning HD with Apple TV. Visit www.itunes.com/festival for more information. Join the conversation using #itunesfestival.