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
Markington ABCDE
Milwich FGHJK
North (B-F)(C-D) H(E+F).(A-C)(C+F)(D-E) West (B-K)(D-E)G (J-K)(D+F).K(E-D)(G-F)