This is the Alix Dress (version 2) by By Hand London. The pattern is designed for wovens but I made it up in a stretch velvet. Since the design is loose fitting it doesn’t really require a knit fabric, but it does make it very comfy. The only change I made to the pattern was to add an inch to the length, since Version 2 comes up quite short as drafted.
Blog post here: https://englishgirlathome.com/2016/12/26/christmas-party-alix-dress/