...and while we're on the subject of illustrators of Algernon Blackwood's work, meet W. Graham Robertson. The image above is the fantastic endpapers that Robertson designed for Blackwood's 1911 novel The Centaur. Remarkably, the design is also reproduced in full as a wrap around blindstamped design for the whole of the cover of the book: front, back and spine. Unfortunately, being stamped in blind rather than in colour or gilt, I've been unable to get a good photo of it.
Graham Walford Robertson (1886-1948) was right at the heart of the 1890s crowd and, among his friends, he numbered Oscar Wilde, Edward Burne-Jones, James Whistler, Walter Crane, Ellen Terry, Sarah Bernhardt and on, and on... in fact, in 1931 he published a memoir titled, Time Was, which wasn't so much a memoir as a chapter on each of his more famous friends (Blackwood doesn't appear in the index). There is a delightful portrait of him at The Tate by John Singer Sargent done when Robertson was 28 and, in a willowy, slightly ethereal kind of way, rather attractive. He illustrated numerous books including at least three for Blackwood. As well as The Centaur, he also illustrated The Lost Valley (1910) which I don't have a copy of and, Pan's Garden. A Volume of Nature Tales (1911) from which I have scanned the frontis below. The illustrations, more like decorations in some way, for Pan's Garden run all through the book in the text and are remarkable for their simplicity. Robertson had an amazing collection of William Blake's illuminated poems and his influence is very clear in all the images for Pan's Garden in particular.