Somber and understated:The Duchess of Cambridge at the Somme Centenary

The Duchess of Cambridge - a woman whoby now is well aware that her every style move will be scrutinized - has a highly consideredapproach to fashion.It might verge on theformulaic but shealways paysclose attention to the significance and mood of the eventshe is attending.

On a poignant visit to France to mark the 100th anniversary of the Battle of the Somme,she choose an elegant but understatedcream lace dress.Commentators quicklytook to social media to point out that The Duchess looked lost against the gravel, but perhaps that was her point.

In a rare departure, Kensington Palace officials declined to reveal to royal correspondents who had designed the Duchess"s outfit.As Katedescribed her visit to Thiepval Memorial as "very moving" and "emotional", it seemed the Palace were keen tokeep the attention on howthe young royals were paying tribute to the 310,486 soldiers who lost their lives in the four month battle there.

It was a tone that was picked up by community of "Kate watchers", usually so keen to be first to identify what The Duchess is wearing.Last night, as The Duchess attended a vigil to remember the fallen soldiers, thewoman behind famed twitter account What Kate Wore declined to comment on her outfit until the ceremony had ended out of a sign of respect.

When she did, it was only to remark that TheDuchess of Cambridge was wearinga new grey zig-zag print coat by Missoni;a classicsilhouette, modernised withinteresting detailing, includingasoft metallic shimmer woven through the fabric and oversizepockets.

But even in this outfit The Duchess has perhaps considered the mood.She took styling cues from Jacqueline Kennedy (later Onassis),buttoning the coat all the way up to the collar and wearing avintage-inspiredblack pillbox hat with a bowat the base by London-based millinersLock Hatters.TheDuchessworea pair of large faux pearl earrings by Balenciaga, a style also reminiscent of Mrs Kennedy.But instead of wearing her hair in a voluminousblow dry like Kennedyfavoured in the 1960s, the Duchess updated the look by pinningher hair back into a low twisted chignon.

This isn"t the first time the Duchess has worn this minimalstyle of hat.She wore a red pill box haton her Australian tour in 2014.Although they were first inventedin the 1930s, and favouredby Crist??balBalenciaga and Christian Dior, it was Kennedywho made this style a go-to forstate dressing, claiming thatshe felt "absurd" wearing fussy, elaborate hats.She turned to Halston, who was workingas a milliner at Bergdorf Goodmans,to create modern pillbox hats for her as a compromise.

Duchess of Cambridge: every outfit ever

Fifty years later, the likes of The Duchess of Cambridge, Carla Bruni-Sakozy andQueen Maxima of the Netherlands are still turning to pillbox hats for formal occasions, where a quieter, sleekerhatis more appropriate than an Ascot-style masterpiece.

Battle of Somme anniversary, in pictures