Robin Jacques
A couple dozen scans here from two books illustrated by Robin Jacques. The first group is from The Case of the Silver Egg, written by Desmond Skirrow and published in 1968. I wasn't familiar with Jacques before I came across these books, but from the samples I've seen elsewhere online, these seem pretty typical of his style. It's nice stuff, with a lot of delicate hand-drawn textures and patterns. Unfortunately, the reproduction in Silver Egg is fairly poor -- much of the linework and detail is flat and smudged; the second group of scans (below) benefit from much better repro.

There's a sort of idealized sameness - even a blankness - to many of Jacques' faces that keeps this stuff from being brilliant, I think. Often the characters don't look as if they're seeing each other, their gazes sort of unmatched and vacant. The kids' faces especially suffer from this.

The remainder of images are from Andre Norton's
Gray Magic, published in 1967. The reproduction here is far superior, and I think the drawings are better as well, strange and elegantly rendered.
I love Jacques' work. Of course the Norton book is an example of the genre in which he was most brilliant -- fantasy, fairy tales, etc. He did all the artwork for 20 or more fairy tale books by Ruth Manning-Sanders. He excels at witches, wizards, dragons, trolls, ogres, giants, devils, all sorts of fantastic creatures.