Gwen Stefani has turned the big 4-0

Kate Beckinsale helped her pal Gwen Stefani celebrate her 40th birthday on Saturday.

The singer held a private party in the Butterfly Room at Cecconi's restaurant in West Hollywood.

‘It was specially decorated for Gwen's celebration with happy birthday balloons and roses,' says a source.

Gwen and Kate seem very close and the girls shared a long chat and many laughs.'

They were joined by Gwen's husband Gavin Rossdale, 43, their kids Kingston, 3, and Zuma, 13 months, and Kate's husband Len Wiseman.

Gwen looked amazing and so much younger than 40,' the source tells People.

‘She was in a great mood and seemed very excited to celebrate her birthday with her husband, children and friends.'

Gwen was later surprised with a birthday cake.

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