Last night, Prince William was solo when he hosted a positively star-studded gala for Ralph Lauren and the Royal Marsden Cancer Charity at Windsor Castle. Despite a guest list that included Ralph himself, Kate Moss, Cate Blanchett, Benedict Cumberbatch, and many more, one important name wasn't on the list: William's wife, the Duchess of Cambridge. Find out why William and Kate may not be side by side at such high-profile events in the coming months.

On Allie: Alice + Olivia skirt, Boden top