When I worked at LCC I did a levelling job out in the sticks for a potential resurfacing scheme, on the proviso that the length had to be re-surveyed prior to work starting as it is known for the ground to swell and contract in height by over a metre over the course of the year, which is why many of the local fen roads are very "uppy downy".
There is one section of road somewhere near Boston (forgive me its nigh on 15 years since I last went down that way so cannot remember exactly where) that was fairly level during the winter months and like a roller coaster in the summer.
Suffice it to say, I found many of the roads much more fun to drive in the summer
And Fenland drivers certainly know that. I imagine that suspension repairs are quite lucrative round there.
Back on track, wasn't there some sort of arrangement involving timbers and animal skins on the Holme section? Replaced with something more modern in the 1980s.