This has absolutely nothing to do with the suit, but clicking on your links was interesting in that we went straight from DM in a restaurant scene with Louisa to DM in a restaurant scene with Edith. I was struck by the difference in his demeanor. With Louisa, his facial expression is softer, more vulnerable, less sure of himself. With Edith, he's all business.
I agree 100% with you Biffpup! Martin with Edith is about medicine (or so he thinks) - all cerebral - hence his shock when she exposes her lacy lingerie.
But with Louisa Martin tries to be softer and gentler, as well as more vulnerable, although at times she should take her brown purse and clout him upside the head! But then he usually puts his foot in it...