I don't remember, but someone here on this site commented that you don't require to use 'prior' (or for that sake 'pre') for booking, appointment, approval, permission etc.
I thought it for a while and admit that that is true!
"You need to have a prior appointment to meet the chief minister" ~ why prior? appointment is appointment, it's always made in advance!
So...
prior booking = booking
prior appointment = appointment
prior approval = approval
prior permission = permission, and so on...
I want to discuss this with the natives here. Is it redundant to use 'prior' in all such cases. Also, can you come up with an example where using 'prior' does make the difference or it's mandatory?