But, if your friend joins his dad on the birthday flight and pays 2/3 of the cost for himself and his dad, it's perfectly legal!
FNG Thanks for your response.
I know a lot of pilots (PPLs and professional) who are uneducated by your criteria. We'll keep 'banging the rocks together'
but, in the meantime, to clear this up, please can you tell us -
What would be the offence which the PPL commited if he took his photographer friend flying on a cost-sharing basis knowing his friend would be selling the photos?
(You can assume I understand, and agree with, the thinking behind what you say the law is. )