Without running a search, I think this is the '57 or '58 annual. The Holy Grail is the 1959 one: John M Burns illustrated the front plate -- he told me it was one of the earliest pieces of pro work he'd done; he bought a couple books on horse anatomy at the time (which he still has!) so that he could do it properly... as a result he now has no fear of drawing horses, unlike some artists.
In the current run of The Order (wot I am currently writing and which John is illustrating) I run a lickle riff / homage to Champion the Wonder Horse (and a respectful nod towards John, of course!) 60 years later.