Tom Cruise and Cameron Diaz raced each other on BBC's Top Gear Thursday in England to promote their flick Knight and Day.
A source on the track -- just outside London -- tells UsMagazine.com, "Cameron and Tom got really competitive about who was going to get the best time."
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As for who beat whom? "Tom is a real pro behind the wheel... Cruise was definitely the best. He knows his stuff. But Cameron... she is feisty and certainly drives with gusto. She didn't like having manual transmission, but she had fun with it. A lot of laughing and a lot of cursing, which will have to be bleeped out."
A network spokesman confirms to Us their episode will air on July 25 on BBC Two in the UK, and in September on BBC America.
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After spending about an hour racing and taping the "Star in a Reasonably Priced Car" challenge (they drove a Kia Cee'd), they sped off to change for their UK premiere -- which starts just two hours later!
Celebs often swing by Top Gear to chat with the hosts and try their luck on the track. This season, Harry Potter star Rupert Grint has the best lap-time of 1:45.5. Simon Cowell, Sienna Miller and Guy Ritchie have also gotten behind the wheel.