It occurs to me that at no point have I addressed that the sitter has a fair bit of hair and a sizable mustache. Just like in life, I'd ignore it for now, otherwise you'll get distracted by it and your portrait will become a caricature. The parts of the head hidden by hair will have to be imagined - a knowledge of anatomy will help with that, but that is for another blog post.
This next phase is further refinement of the head and features. If you look at stage two and three next to one another, you can see some slight yet significant changes, primarily to the lower nose and mouth area. At this point it is good to begin looking at features as they relate to each other. The base of the nose relative to the root of the nose was more closely examined and adjusted. The distance between the nose and mouth was increased, the nostrils were widened, the jaw was pushed out slightly. His ear was made less generic. Since I already had the eyelids estimated previously, I started to pay closer attention to the sagging skin under Patmore's eyes. Those bags of flesh should hang right off of the bone, so if your sockets are placed correctly, then it should fall into place. If we did our job right in the first stage, then all of these changes should be small, but great in number. The combination will be profound. Again, if you think about the centerline and what it is doing, it will help guide you.