Neither had heard of the other before! Tolkien wrote to his son Michael about their meeting in Letter 267, describing the film star as "a pleasant young woman", "well but quietly dressed, easy and agreeable", with whom he got on well. Professor Robert Graves introduced them to each other, and only when JRRT was told of her fame did he realize that "the press of pressmen and storm of flash-bulbs on the steps of the Schools were not directed at Graves (and cert. not at me) but at her..."
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'Mercy!' cried Gandalf. 'If the giving of information is to be the cure of your inquisitiveness, I shall spend all the rest of my days in answering you. What more do you want to know?' 'The whole history of Middle-earth..
.'