Cocooned...?

Never seen one like this before, found inside a clump of santolina in our herb bed, and measuring about 30mm across. We have some interesting hawkmoths in this part of France, as well as the great peacock moth which is huge, so perhaps it's one of these? But my knowledge of moths and butterflies is very limited as I don't really know the difference between a pupa, a chrysalis and a cocoon - and actually this might be none of those.

It's slightly scary waiting for something (or several things) to come out!!