'A letter?' repeated Professor McGonagall faintly, sitting back down on the wall. 'Really, Dumbledore, you think you can explain all this in a letter? These people will never understand him! He'll be famous - a legend - I wouldn't be surprised if today was known as Harry Potter day in future - there will be books written about Harry - every child in our world will know his name!'
I wonder if when she wrote this, J K Rowling realized just how true this was going to be.