Katy Perry closes iTunes Festival
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."
Last week the 28-year-old told Billboard magazine the song was "evident of how tough" her divorce had been.
"I asked myself, 'Do I want to endure? Should I continue living?'" she was quoted as saying.
In the song she credits her sister, Angela Hudson, with helping her combat depression after Brand filed for divorce.
"Thank my sister for keeping my head above the water - when the truth was like swallowing sand," she sings in the second verse.
Although sombre, the song ended on a positive note in keeping with Perry's life-affirming pop standards Firework and Teenage Dream.
Both tracks formed part of the singer's brisk, 45-minute set, which saw her race through such breezy teen anthems as Part of Me and California Gurls and perform a rock version of her breakthrough hit I Kissed a Girl.
The star took to the stage in a tartan skirt to play a new dance track, Walking on Air, from her forthcoming album Prism.
Aided by four industrial wind machines, she sang the chorus wrapped in a billowing white sheet.
Throughout the singer was supported by nine dancers dressed in baggy dungarees (for the boys) and cut-off denim shorts (for the girls).
Her band was augmented by an eight-piece string section, which took part in a slow-burning version of her 2010 hit Firework.
The acoustic treatment of the song revealed Perry's limitations as a vocalist as she strained to deliver the ascending melody that builds to the chorus.
Yet she was in fine voice for her current single and set-closer Roar - a song about battling your demons, performed while skipping in a leather skirt that lit up with images of an animated tiger.
The staging encapsulated the star's two prevailing themes, affirmation and playfulness.
"Thank you, London," she told the fans she calls "kitty cats" as she left the stage. "I've had a fantastic time."
Perry's show drew the curtain on this year's iTunes Festival, which has occupied the Roundhouse in Camden, north London for the last month.
Arctic Monkeys, Jessie J, Sir Elton John and Kings of Leon also played at the event, which was launched by Lady Gaga on 1 September.