Claudia's dress is a stunning Livonia dress by Unique, available at Topshop.
Here's the description - Metallic lamé gives a nod to the '80s with this shiny, smooth dress. Cut with a high neck and a revealing open back, the dress includes a silk slip and comes with an exaggerated belt waist to cinch the silhouette in. Includes a slashed split to the hem for a flash of leg and fastens with a zip closure. By Unique. 100% Polyester. Dry clean only.