The hotel heiress exchanged her vows at Kensington Palace's The Orangery in the haute couture dress, which designers Maria Grazia Chiuri and Pierpaolo Piccioli made from "precious vintage lace", "three different tones of ivory" and "richly embellished crystals".
The official Instagram for Valentino posted a description of the lavish wedding outfit.
They wrote, "(The gown) was composed with three different tones of ivory and silver guipure richly embellished with crystals.
"The high neck bodice stitched to a precious balloon skirt ending with a three meter long train. Covered with a long veil is enriched all around the edge with a precious vintage lace (sic).