The actress put on a rather leggy display with a sheer lavender gown with ruffles that flowed all the way down to the Cannes red carpet.

Underneath the dress, Sienna wore a plunging playsuit to reveal a glimpse of her long legs and slim figure.

Her silver heels also gave her a few inches of height next to her tall and slim boyfriend Oli, who sharp black suit and tie and a pair of shades.

She completed the look with a sparkling diamond necklace, adding an appropriately glamorous final flourish…