Victoria Beckham is planning a horse-themed party for her 40th birthday.

The fashion designer, who will celebrate the milestone on April 17, has joined a riding club in Los Angeles and is reportedly planning to gallop around the Hollywood Hills with friends to mark her big day.

A source told the Daily Mirror newspaper: ''Victoria actually went riding properly for the first time a couple of years ago and loved it. But over the past few months she has stepped things up a notch and got really good.

''Obviously she can't keep a horse in her back garden in west London, but when she is in LA, which is around once every five or six weeks, she goes riding daily in the hills.

''Not only is it great exercise, but in her helmet Victoria can go about largely unnoticed.''

The 39-year-old star, who has children Brooklyn, 14, Romeo 11, Cruz, eight, and Harper, two, with husband David, is reportedly having two birthday bashes in Los Angeles and London, with the US celebration being an afternoon out in the hills horse-riding with her pals, including actress Eva Longoria and hairdresser Ken Paves.

The source added: ''The evening do is dinner out at Eva's restaurant Beso, with most of Victoria and David's Hollywood chums, including the Ramsays - Gordon and Tana. She is also having a civilised family dinner party at home in London, which her mum is helping to organise.

''Gordon will probably be roped in to do the cooking. And obviously David, the boys and Harper are planning their own surprise.''