I struggled a bit with the first few sips trying to decide too sweet, not enough bitterness, etc. Rereading Difford's description and recipe thinking about how I might modify, I realized I had forgotten to express oils from an orange garnish. Doing so for the rest of the drink was a revelation. This drink requires this and definitely elevates it. Having said that, I'm not sure I will add it to my "Favourite Collection" until I contrast this with the more bitter Old Pal version.
Agreed, I was wavering over adding a dash of angostura, but left well alone in the end and added an extra zesty spray instead. I think vermouth di Torino and high abv rye are key here for those of us who are used to and appreciate a heavy duty Manhattan etc.