geordies spotting the players post

[McIvan]

I would think that someone well familiar with a scenario should tell their opponent without being asked, and warn them to have a thorough look themselves or pick another scenario. Their opponent may or may not care, but they should at least have the information. To have played a scenario many many times and keep quiet about it against someone who (on the face of it) has not, is certainly not cheating but is very gamey.