Knight carefully removed Jill’s plaits in several editions of Jill’s Riding Club. The alterations are there in the 1970s W D Underwood cover version, and the Red Rosette and White Spine editions. Jill’s Riding Club, in common with all the other titles, lost all illustrations in the Black Horseshoe edition, so that was the end of those alterations. I haven’t (yet) found any other title which had the illustrations altered, but that doesn’t mean it didn’t happen. I haven’t read every title in every edition. If you do find any deviations, please let me know. Knight weren’t selectively anti-plait: May Cholly-Sawcutt also has her plaits removed. Long flowing hair was considered ok, and this was left. There are some illustrations where it was obviously tricky to remove the plaits, so Jill is left with a sort of long ribbon effect, which I actually rather like.. I suppose this was an attempt to update the books: in the only other title which retained the Caney internal illustrations, Jill and the Perfect Pony, Jill has had her hair cut in the books, and presumably the hairstyle passed muster.
The Anti-Plaitist League
Left - the original Caney, and right, as altered in the Knight paperback printings
Left - the original Caney, and right, as altered in the Knight paperback printings
Even poor May lost her plaits. Left - Caney original Right - Knight