There are so many titles to keep track of: Administrative assistant, PA, Executive secretary, and of course the Private Secretary (PS). When it comes to titles, it can be a bit of a semantic argument; and, in this case, the country matters too.
Generally speaking, the term Private Secretary is primarily used in the United Kingdom, and not so much in the United States. According to the official website of the British royal family: "The Private Secretary is responsible for supporting The Queen in her duties as Head of State." In this specific case, that role currently belongs to Sir Edward Young.
On the Law Insider website, a private secretary is an individual who works for someone elected or appointed and works in an administrative capacity: handling communications, filing duties, calendar management, etc.
Is it old fashioned to use the word secretary?
While it is true that the word "secretary" is a bit antiqued, it's not surprising to see that it's still used by the royal family in the United Kingdom because they do like to hold onto tradition. In the United States, we mostly use the title Executive Assistant. If the role is a hybrid position working in a private estate, then the term PA or Executive Personal Assistant may be used.
Written for assistants and estate managers working for celebrities, CEOs, UHNW families, billionaires and royalty