The singer, whose actual birthday is Oct. 3, was joined by her hubby Gavin Rossdale, their two children – Kingston, 3, and Zuma, 13 months – and an intimate group of friends, including Kate Beckinsale and her husband Len Wiseman.
The celebration took place in the restaurant's romantic and private Butterfly Room, which features a $1 million heart shaped Damien Hirst painting and a crystal chandelier. "The Butterfly Room was specially decorated for Gwen's celebration with happy birthday balloons and roses," says a restaurant source.
The group enjoyed a family style lunch with several Italian appetizers, pasta dishes, salad, champagne and wine.
"Gwen looked amazing and so much younger than 40. She was in a great mood and seemed very excited to celebrate her birthday with her husband, children and friends," says the source. "Gwen and Kate seem very close and the girls shared a long chat and many laughs. Gavin and a nanny took care of the boys so Gwen could just relax and enjoy her celebration."
After a long Italian feast, Gwen was surprised with a big birthday cake decorated with candles and sparklers. "With her oldest son helping her to blow out the candles, Gwen made a wish and she looked very happy," the source adds.
Stefani's birthday celebration actually started the night before when she and Rossdale enjoyed a night out without their kids during a party at the Oceana Hotel in Santa Monica. "Gwen and Gavin spent a great night with friends and looked very happy together," says a hotel source. "When the clock struck midnight, Gwen and Gavin toasted to Gwen's big birthday."
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