XS UK 8 - however like most ‘robes’ this comes up quite big so would comfortably fit up to a UK 12 (I’m approx 14 and can zip it up)
This is new - has only been tried on. Has a couple light dust marks from storage and tiny drabs of hay inside from being transported. 
Does have a manufacturing fault - zip inside coat has been put on inside out meaning you cannot zip it up. The coat itself zips up fine. Would benefit either replacing the zip or throwing some stitches in to close up the gap inside. Otherwise doesn’t affect use! Half of RRP.