@psyclist I rode the first 53km of the route today with fairly flattish routes to / from home. Overall climb figure of 14.93m per km. This is from my GPS which has a barometer for altitude. So I’m fairly certain the middle bit I plotted will exceed 15m / km. it’s in line with what bike hike came up with.
Entirely in Herts though it does come within metres of Bedfordshire , just a hedge separating them, at end of Luton airport runway.
One 17%, one 15%, one 11%, two 10%, and numerous 6-7% hills.

So definitely looking good for you to incorporate, once audax restarts again. Not as complex as it looks, as this includes my to and from which intersected the route.