Blonde hair flying she careered around the Main Stage at the former Ebrington army barracks in Londonderry, her energetic show included drumming and characteristic indie-pop vocals.
She played at the royal wedding reception in 2011 for the Duke and Duchess of Cambridge but said it all began with Radio 1.
"To play Radio 1's Big Weekend is an honour," she said. "Radio 1 has supported me from the very beginning. My first single I ever put out they played on the radio and every single DJ has supported me 100%. I feel lucky to have Radio 1 support."
She said she learned the drums to "take her passion out on" after a seemingly spontaneous performance in Derry but paid tribute to her tutor.
Scottish rock trio Biffy Clyro were the main stage headliners tonight. The band's support slots for Bon Jovi have led to sold-out gigs at London's O2 arena, a successful sixth album, Opposites, and now a headline set in Derry. They include lead vocalist Simon Neil, bass player James Johnston and drummer Ben Johnston.
The outfit played on a stage dramatically framed by the church spires and riverscape of Derry as well as the serpentine Peace Bridge, opened to symbolise the city's efforts to bridge the gap between nationalists and unionists. Neil said: "This venue is a spectacular place, it is just such a beautiful part of the world and great to be part of the City of Culture and for Radio 1 to host this is an amazing event."
He reflected on topping the bill. "It is a different kind of pressure but at least the people you are playing to are familiar with your band so that pressure is removed but you are aware that you are ending the day for people and that you need to go out on a high," he added.
The Saturdays lit up the Main Stage earlier. Flamboyant dance routines and a lively performance of their new single Gentleman met an enthusiastic reception.
The festival is being held at the former barracks in the city to coincide with its year as City of Culture. Thousands of people will attend the three-day long show which kicked off on Friday with performers like Calvin Harris.
COMMENT RULES: Comments that are judged to be defamatory, abusive or in bad taste are not acceptable and contributors who consistently fall below certain criteria will be permanently blacklisted. The moderator will not enter into debate with individual contributors and the moderator’s decision is final. It is Belfast Telegraph policy to close comments on court cases, tribunals and active legal investigations. We may also close comments on articles which are being targeted for abuse. Problems with commenting? email@example.com