I've just run it through my Memory Map with proper charts and surprisingly it is 95 miles if you keep very close in at Portland and only a couple of miles longer (97 miles) if you keep 7 miles south of the "Old Bill".
Not taking tides into consideration of course.
So it does. It's a bit well-hidden though, isn't it? Still, in fairness, it's probably easier to use than the daftlogic one I've been using until now...