2019 sees the centenary of the ending of WW1 and 75 years since D;Day during WW2. The series has been placed with this, in mind.
The difficulty rating is a mix of the puzzle and the final location.
At each final there is enough room for a single car to pull over to allow room for a car to pass, if you are sensible.
The only hint for the series is at No1 for the puzzle
Now for the puzzle
Belper ABCDE
Colbury FGHJK
North D(A-J) (B+C)K.(A-C)(G+H)((F+H) West (A-C)(G-J)(B-A) H(B-E).(E-H)(K+J)(D+F)