Sorry but if that's the case, then they are idiots Checking the NOTAMS should be as automatic as checking the weather.
I know they can be a pain to get, but at least get the departure and destination and diversion NOTAMS.
That way you aren't relying on anyone else to do your work for you. Why should a controller check whether you have a slot? It may just be a data input monkey rather than anyone qualified. How are they to know you haven't got a slot?
Sorry, but there are no real excuses on that one. Even the most junior PPL trainee should know to check NOTAMS.If their FI doesn't mention it (which of course they should) then even a cursory glance at an air law course book will tell you.
Sorry SB, but I can't see much of a defence really. As Traffic Police are so fond of saying "ignorance of the rules is no excuse, Sir"