HapooPrimrose Hill
Small, steep, and almost entirely about the view from the top, which takes in most of central London and is worth the four minutes it takes to get up there. Not a long walk. A very good short one.
Hapoo counts the walk you were doing anyway
Read off your phone's motion sensor after the fact, so there is no start button and nothing running in your pocket. Characters turn up at real park gates across London, this one included.
