She does always look really nice in Jenny Packham! Don’t remember many green evening gowns that she’s worn but this one has a nice light, “foamy, etherealness” to it that Kate does so well.
She has a couple, at least (I nerdily know because they are two of my favourites!):
This Alexander McQueen one, worn once to BBC Sports Personality of the Year
and this lovely Temperley one
and there's the green sequin one she wore in Pakistan