Their or his/her

I have just written a book review for Education Review. In it I had to face the problem of using "his or her" or "their".

It was once the case that "he" would be accepted. So that "Everyone in the nunnery was expected to do his best" was regarded as good grammar even if totally bonkers!
Now generally we have a choice:

Everyone wants to do his or her best.

or

Everyone wants to do their best.

Although the second sentence violates the general rule requiring agreement with the antecedents, many writers and speakers prefer to use forms of they because these forms are not gender specific. This is a common practice, but it is still criticized by grammatical purists.

And of course, Shakespeare, Jane Austen, Walt Whitman and the King James' Bible all used "their" as a gender neutral singular or plural possessive pronoun.

So "their" it was :)