Katy Perry closes iTunes Festival

Katy Perry (centre) with her dancers
US singer Katy Perry has brought this year's iTunes Festival to a close in London with a brief set that included the first performance of a song about her divorce from comic Russell Brand.
By the Grace of God describes how the pop star overcame thoughts of suicide after her marriage ended in 2011."I looked in the mirror and decided to stay,"she sang as the track ended.After performing the ballad at Camden's Roundhouse,Perry raised her hand and said: "Thanks for letting me stay."