Catalogue of the Well-Known Collection of Autograph Letters, Historical Documents and Signed Photographs Formed Between 1930 and 1979 by the Late R.E.D. Rawlins Esq.
2-4 June 1980.
Sotheby's.
Paperback.
Hammond p.387.

Lot 1231 reproduces in facsimile an autograph statement by Tolkien "In all my works I take the part of the trees as against all their enemies".  This is an excerpt from Tolkien's 1972 letter to The Daily Telegraph.  It can also be found in The Letters of J.R.R. Tolkien.