I'm surprised no one's mentioned Shirin Guild here. She is an Iranian-English designer who has been making minimal, box-based garments with interesting materials (like silk/steel blends) since the early 90's. The V&A has one of her ensembles in their permanent collection:
Also, this photographer did one of her look books. Comfy-looking stuff. : )
Also, this photographer did one of her look books. Comfy-looking stuff. : )