Right engine
12hrfdp reporting before 0600
Problem is the rest of Europe has been doing this (safely?) for many many years.
I can't see however much discretion being used though.
Lastly don't forget airlines can derogate round ease limits much like they could cap371.
If BA pilots want to work/swap so they can do back to backs so they can get nice runs of days off all they need to do is come up with a safety case. You can bet no one will mention the F word....