Kate Middleton in blue polka dot dress by Alessandra Rich for Big Lunch

William and Kate surprised locals by dropping in on a street party in Kensington, London on Sunday. The Duchess looked beautiful in a blue polka dot dress

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Kate Middleton in blue polka dot dress by Alessandra Rich for Big Lunch

Kate Middleton's Polka Dot Looks in Photos

Kate's go-to designer Alessandra Rich delivers her verdict on the royal's style moments

Kate Middleton's Alessandra Rich Azure Blue Polka Dot Dress

Meet Alessandra Rich, the Duchess of Cambridge's new go-to designer

Kate Middleton's dress today: Dupes of the Alessandra Rich polka dot gown