Typical idiot council (this comment has nothing to do with the lorry, bye the way). That sign looks like an advert, so it will be frequently ignored, and the important part is in smaller writing.
It should just be a simple sign:
!
WARNING
Harbour has steep walls (over 5 metres high).
THERE ARE NO LADDERS OR EXIT STEPS!
YOU MIGHT NOT GET OUT.
Doddery old fool.