Katy Perry closed the iTunes festival in London last night (30.09.13).

The singer took to the stage at the Roundhouse to end the month-long event with a 45-minute set of her biggest hits and some new tracks from her forthcoming album 'Prism'.

Opening with new song 'Walking on Air', Katy - who performed with nine backing dancers - then launched into 'California Gurls', 'Teenage Dreams' and 'I Kissed a Girl' before treating fans to another new track, the uptempo 'Dark Horse'.

She later showcased another song from 'Prism', 'By The Grace of God', a piano-backed track about her failed marriage to comic Russell Brand.

The brunette beauty - who changed outfits twice during the 10-song performance - rounded off the show with a stripped-down rendition of 'Firework', backed by a string section, and her recent number one single 'Roar', which she sang from inside a mock boxing ring.

Leaving the stage, she said: ''Thank you London, I've had a fantastic time.''

Meanwhile, Katy has announced the tracklisting for 'Prism', which is released on October 18.

Tracklist for Prism:

1. 'Roar'

2. 'Legendary Lovers'

3. 'Birthday'

4. 'Walking On Air'

5. 'Unconditionally'

6. 'Dark Horse' (feat. Juicy J)

7. 'This Is How We Do'

8. 'International Smile'

9. 'Ghost'

10. 'Love Me This'

11. 'Moment'

12. 'Double Rainbow'

13. 'By the Grace of God'

14. 'Spiritual'

15. 'It Takes Two'

16. 'Choose Your Battles'