While Goldie Hawn's daughter put on the glitz in figure-hugging sequins, the Devil Wears Prada star downplayed her good looks with a more demure, sophisticated appearance.
And thanks to a statement-making ponytail cascading from her crown that had height and body enough to flatter any face shape, we think Ms Hathaway just pipped Kate to the post in the style stakes.
You need a hairpiece to get this look – try Hot Hair, which has concessions at Topshop, Selfridges and Debenhams and is available online at www.hothair.co.uk.
The Xpress, £38.17, is a ready-formed long ponytail that you simply attach around your own ponytail – however short it may be – to create the impression that your own hair's as thick and luxurious as a thoroughbred's mane.
Make sure your hair's scraped back into as high a position on the crown as possible – smooth it down against the scalp with hairspray for glossy shine.
Backcomb your own ponytail before securing the hair piece – the effect needs to be almost bouffant to create that retro feel.
Then backcomb the under sections of the hairpiece near the base – synthetic hair knots easily so you need to leave the visible top sections smooth.
Using a brush lightly backcomb the length of the ponytail, too, so it fans out to create that sheet of hair behind the head.
Use fabric conditioner to ease out the knots once you've finished with the hairpiece.