Machiavellian line penned by children's author (7)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

L in POTTER Beatrix Potter, duh. I was thinking, in what world is Harry Potter a children’s author? Never mind that I read all the Beatrix Potter stories as a child, and have never read any of the Harry Potter books… My problem here was the definition. Did not know that Machiavellian could be a noun, but of course it seems obvious now.