n an editorial on the government’s new climate target, we wrote of “Mr Johnson’s newly-donned green clothes”, and of the UK’s “existing, legally-binding, target to achieve net zero greenhouse gas emissions by 2050”. It has never been our style to use a hyphen after words ending in “-ly”.
I don’t know if there is some reason in formal grammar for this, but I have always told myself that the “-ly” acts as a hyphen, because the point of it is to connect with the word that follows it.
In any case, our policy in recent years has been to eschew hyphens altogether, unless they are needed to avoid ambiguity. Old habits persist, however, and it is quite hard to train journalists out of referring to people by their age, so we often write things like “the 58-year-old said”, when “the 58 year old said” is just as good and less hypheny.