I thought I'd better flesh out my last posting:
The anthology to which I referred was
The Monsters and the Critics and Other Essays (HarperCollins, 1997), which comprises the following:
The Monsters and the Critics obviously
Sir Gawain and the Green Knight (Ker Memorial Lecture, University of Glasgow, 1953)
On Fairy-Stories (University of St. Andrews, 1939)
English and Welsh (Oxford, 21 Oct 1955 - this is the post-RoTK lecture I mentioned, but you all knew that.)
A Secret Vice (1931 - Contains some early Elvish poetry!)
and Tolkien's Valedictory Address (delivered at Merton College, Oxford, 1959)
The imperative I quoted is from
The University of Virginia
Apologies to those who knew all or most of that already.