v6 p3
~50%
“He’s illiterate and old, as is every custodian that has ever been employed to manage the royal archive. Frankly, I find it a questionable practice, but an illiterate custodian cannot disseminate the contents of the archive to the outside world. And an old custodian is more or less a guarantee they can’t learn how to read even if they wanted to. That they would go so far speaks volumes about the secrets being kept here.”
Something awkward about the grammar here -- an old custodian isn't a guarantee, rather employing an old custodian is a guarantee. And the the singular "old custodian" clashes with the with the plural "they can't" IMO. Maybe that was intended to be a gender-neutral "they", but as an alternative:
And an old custodian is more or less guaranteed to be unable to learn to read even given the desire to do so.