"Noone" *has* to be an error (unless it's Samuel Pepys telling the time, perhaps) because "oo" is not the same as "o o". Thinking about it, maybe "no-one" versus "no one" differentiates a "negative entity" (to coin a phrase) from a count. If you said "no one", it would make more sense in the context of "no one termite destroys a building, but a million of them will".

But given the number of bizarre constructions in English, it ain't necessarily so. :-/ And I agree that "no one" is normally perfectly clear in context - it just happens that I learnt it as "no-one".

Graham.

PS. Rowan, I'd heard the joke as "eats, roots, shoots and leaves" and involving a panda, long before Truss's book (although long after 1952! ;-). I just assumed she'd bowdlerised the joke for publication.