Soccer player David Beckham and his wife Victoria arrive at the 2008 ESPY Awards in Los Angeles, California July 16, 2008. [Agencies]

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David Beckham's sons are avid UFO spotters. The soccer star's friend Robbie Williams - who has previously admitted he is fascinated by UFOs - heard about nine-year-old Brooklyn, five-year-old Romeo and three-year-old Cruz's passion and has made it his mission to ensure they have a close encounter of the third kind.

Whenever Robbie hears that an unidentified object has been seen above Los Angeles, he phones David so he can take his sons to see it.

A source said: "The boys are fascinated by aliens and flying saucers and are desperate to see some. When Robbie heard about their love of UFOs he promised to tip David off.

When the call comes, David and the boys rush into the Hollywood Hills to try to spot spooky lights." However, Robbie's efforts do not always go according to plan. The source added to Britain's Daily Star newspaper: "After a tip from Robbie a few days ago, David took the boys to the Madeo restaurant to wait for a call saying some strange lights had been seen in the hills.

But it was getting really late, and while they waited, Cruz fell asleep at the table." Robbie has been a believer in alien life forms for years and recently attended a UFO convention in Nevada.