Gerard Butler sings with Mayer

The Scottish actor turned 41 on Saturday and marked the event by holding a dinner accompanied by cabaret acts, singing and dancing at The Derby restaurant in New York.

Among the most distinctive of his performances was a duet of Mustang Sally with American musician John Mayer. Gerard surprised the crowd, including Bono and Jay-Z, with his excellent vocal skills.

"Gerry also sang Oasis hit Wonderwall with Lady Rizo and Mayer played guitar. They then followed it up with Mustang Sally,” a source told the New York Post. “He had a pretty good voice - it wasn't what you'd expect from the guy from movie 300. It was epic. He was also in the DJ booth a lot and got the DJ to play a lot of rock, 80s and funk.”

The rugged star was not afraid to show off the sound of his pipes, giving each performance his all. He was in the mood to have fun, and laughed along when his hectic party lifestyle was mocked during the evening.

"Australian comedian James Smith toasted Gerry. He then went on to make fun of him saying, 'Gerard has been out so much he's now just constantly on [US gossip column] Page Six. Gerry is on Page Six so much they have to make it Page Seven,'” a source said.

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