The Grammy-winning singer Adele, actors Benedict Cumberbatch and Elizabeth McGovern were among the audience at London's Roundhouse on Sunday night.
"Star Trek" stars Chris Pine and Alice Eve plus TV chef Jamie Oliver also watched Timberlake mix fresh songs from his new album, "The 20/20 Experience 2 Of 2," with favorites like "Cry Me A River" and "SexyBack."
Timberlake called London crowds the best in the world and joked that he was getting too old for it, when he was too sweaty to talk on stage.
Katy Perry closes the iTunes Festival on Monday night.
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