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She chatted warmly with the racing driver, who gave her a kiss on the cheek.
He seemed to be admiring her jacket, which was printed with images of spectators watching the Monaco Grand Prix.
As a former Olympic swimmer, Charlene no doubt welcomed the chance to converse with a fellow sports figure.
Michael had joined the blonde royal's husband and their niece Princess Alexandra for a kickabout in Monaco.
The youngster is Princess Caroline's 12-year-old daughter with her estranged husband, Prince Ernst of Hanover.
Watching the action with Charlene from the stands were Princess Stephanie and her pretty 18-year-old daughter Pauline Ducruet.
With the Grand Prix taking place on Sunday, excitement is building in the principality.
The day after the football, Albert hosted a glam gala for visiting celebs.
Stars dressed up to the nines for the posh event included Diane Kruger and her boyfriend Joshua Jackson.
Former US president Bill Clinton was also in town.
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It's a little princess!