Originally Posted by
NA-Flyer
It was mentioned in many places that BA has started chasing travelers who skip the last sector on discounted or promotional fares in premium classes.
While that may be true, it does not create a legal basis to charge anyone more for flying less.
There have been numerous court rulings (Germany and Switzerland come to mind) that show that airlines can't make you pay more for using only part of your ticket. This would even cover a case of not flying the
first segment of a reservation, never mind the last one.
There is a handy cheat sheet on this subject
here (in German).