I think James D'Arcy might come closest of current actors I can think of--he could definitely get within shouting distance, particularly for the earlier cases.

Oh, damn, he didn't cross my mind, but he is a strong contender. It's something about the mouth. Thank you!

It's kind of wild to know that he's currently the same age as Peter in Gaudy Night.

I measure my age by fictional characters and at my last birthday realized I was as old as Peter at the start of Strong Poison, which was pretty wild to me.