Sienna Miller wears the Dior Gaucho © Sipa

How do you tell a real style icon from a pretender? Well, a true fashionista always has her 'it' bag of choice on display right from day one of the new season - donated, of course, by cooing designers eager to see their creations adorning the arms of A-listers anywhere there's a camera lens in sight.

We bring you a sneak preview of the must-have 'it' bags for spring/summer 2008, and the stars who are already ahead of the fashion pack. Now if we could just find a designer who'll give us one for free...