Mrs Cameron, who has been made an ambassador for British fashion, highlighted her “passion” for clothes as she spoke at Somerset House yesterday on the first day of the biannual event.
She kept her outfit British with a Mulberry dress and Sykes jacket, but was not wearing her wedding ring.
Mrs Cameron said: “I am passionate about fashion and it’s a real honour to be here as an ambassador for the British Fashion Council.”
The event kicked off with a show by Paul Costelloe, which featured a host of colourful tweeds and metallic fabrics.
A soundtrack of 1960s music played as models took to the catwalk in tailored swing jackets and flirty skirts.
Around 200 designers will show their collections for autumn/winter 2011 over the next six days, attracting an estimated 5,000 visitors.