Patmore's most distinguishing features are his hair and outfit, some of which are initially sketched in here. His hair is pretty unhinged, and Sargent did a great job capturing it without looking too much like Christopher Lloyd in Back to the Future. I find that when it comes to drawing hair, many people tend to make too much of it. Except in extreme situations, the shape of the skull should still be suggested under the hair, and it should really only take profound form once it has cascaded away from the head versus when it emerges directly from it. Otherwise it will look like your sitter is wearing a wig.
I also laid in the shape of his outfit, keeping in mind his shoulders. With the exception of padded shoulders in the 1980's, you don't want to add to much bulk on to someone's shoulders simply because they are wearing a jacket. Keep it subtle and let their actual posture show through.
Not much was changed about the face here - I was fairly confident that things were placed about as correctly as they could be. Once value is added, however, I may decide otherwise. The addition of tone can change how everything fits together, as you'll soon see.