Justin Timberlake joins Jay-Z joins during Wireless Festival set

Justin Timberlake returned a favor to Jay-Z by joining the rapper onstage during his set at London's Wireless Festival on Saturday night (13Jul13).

The 99 Problems hitmaker showed up unannounced when Timberlake performed at London's Olympic Park on Friday (12Jul13) at the start of the weekend (12-14Jul13)-long bash, and the rapper took to the stage the following night for his own headline set.

Jay-Z performed songs from his new album Magna Carta Holy Grail and he was overwhelmed by the response from the crowd.

He declared, "You could have been anywhere else in the world tonight and you chose here, we appreciate that."

The hip-hop star played a hits-filled set before Timberlake appeared to close out the show by duetting on Jay-Z's track Holy Grail.

The Wireless Festival's second night also featured sets from Miguel, Kendrick Lamar, Rita Ora and Emeli Sande.

Timberlake and Jay-Z are teaming up again officially on Sunday (14Jul13) to wrap up the festival as joint headliners Legends Of The Summer.