One Direction and Usher to play London iTunes festival

One Direction, Usher and Jack White are among the first artists confirmed to play this year's iTunes festival.

The month-long series of gigs, held at Camden Roundhouse, London, have been moved this year from July to September.

"Every year we see some of our favourite bands and artists on the bill so to be part of the line up this year is obviously incredibly exciting," said Harry Styles from One Direction.

The boy band will take to the stage on 20 September.

Usher will kick off the event by performing on 1 September.

Jack White - who recently scored a number one album in the UK and US with his debut solo offering Blunderbuss - will play on 8 September.

Norah Jones has also joined the list of confirmed performers.

Coldplay and Foo Fighters were among the artists who headlined gigs for the series in 2011.

Fans will be able to apply for free tickets through iTunes.