The White Company Navy Blue Linen Frill Trim Dress.
They say:

What We Love

With the option to wear it three ways, this dress is a true multitasker. Crafted from linen, opt to wear it Bardot-style, with the frill to the top off both your shoulders, asymmetrically, or on the shoulders, with the top section acting as pretty flutter sleeves.

100% linen
Machine wash
Label size UK14.
Measurements of the garment: Armpit to armpit - 23'' (stretched), Length (armpit to hem) - 28''.
This dress is in excellent condition. From a smoke and pet free home.
Thank you for looking!