What breaks the enchantment?

[Bêthberry]

Originally Posted by davem

But Gandalf, as an Ainur, would, it seems to me, in this situation,adopt the role of 'impartial' narrator, passing on information to other council members. He can also seem as if he is 'bragging' in the Council, reporting his 'clever' responses to Saruman. I think he is being quite impartial. We have to keep in mind his true nature, & I think if we do his speech is in character. He may be in Middle earth, but he is not of it. As Tolkien put it he is effectively an 'incarnate angel'.

Really? Do readers of LotR know that Gandalf is an Ainur, and indeed what an Ainur is at this point of the story?

Was Gandalf called an 'incarnate angel' in the story or in the Letters?

In short, how do we know what his 'true nature' is at this point in the story?