The fashion designer flew from LAX to her Spice Girls event in London in a caped trench coat by Junya Watanabe Comme des Garçons, which she wore as a dress.
Over in New York on Thursday, Rose Byrne was spotted at the season 5 premiere for Damages looking beautifully prim in a white, knee-length Valentino dress, accessorised with black Valentino clutch and shoes and ruby red lips.
Rihanna made the rather bold choice of a red and pink Acne tuxedo for a walk in London - an outfit which was redeemed by her brilliant Simone Rocha glass-heeled brogues.
Caroline Sieber went for the winning combination of girly pale frock and rocky black gladiator sandals to attend Londons Serpentine party. She was joined at the annual fixture on the social calendar by Azealia Banks, Josephine de la Baume and Erin OConnor.
Princess Beatrice earned a gold star for fashion kudos in a cream Roksanda Ilincic dress set off with quirky blue cuffs and matching satin shoes at the VIP launch of Britain Creates 2012: Fashion & Art Collusion.
Meanwhile, Blake Lively oozed the Old Hollywood glamour of a true starlet in a contoured Zuhair Murad full length gown.
And finally, not to be outdone by her fashionista former bandmate, Mel C picked an elegant Acne number in white for the girl power reunion.
Click through the gallery above to see more of this weeks best dressedMore