I'm sure there are reasons that can be made to sound as plausible as they need to but this isn't rocket science is it? The whole ticketing thing came about in anticipation of much greater interest and demand at the time of the 20th anniversary.
Five years later it should be REALLY simple.
"Hmmm. At least as many as came to the 20th will come to the 25th ergo let's plan to open up pretty much the whole ground, steward on that basis and just open the doors. Tickets not required, just monitoring of numbers coming in......"
Or is that too idealistic of me?
I really hope nobody tomorrow ends up being turned away.