Jim Broadbent, the actor who plays archmaester Ebrose in GoT, also plays Professor Slughorn in the Harry Potter movies.
And in both series he seems to be the overlord of secret and restricted books.
In the first episode of the seventh season of GoT, Samwell Tarly (the former steward of the Night’s Watch who’s now slumming it at The Citadel) is training to become a Maester, so he can learn about the White Walkers.
However, the only information about them is hidden in a restricted area in the library and Samwell Tarly has to ask archmaester Ebrose (played by Jim Broadbent) for permission to see it.
Funnily enough, Broadbent acted out pretty much in the same scene in Harry Potter and The Half-Blood Prince. In a flashback scene, Tom Riddle (young Voldemort, played by Frank Dillane) asks Professor Slughorn permission to look in a restricted section of the library to learn about horcruxes.
Yep, they're both called the 'restricted section' and in both scenes Broadbent's characters are a little hesitant about giving Tarly and Riddle access to them.
— ami (@essence_me) July 17, 2017