With Antthony tops I am always a S ( usually a size 12 or small 14 on the high street) I'd say M for size 14 and large for size 16.
I'm not going for this as I already have enough tops. I've noticed he has brought out more colours of his viscose vests (2 pack on introductory offer) these are great imo, I love them and own almost all the colour sets he has done so far!
