I've filled in the grid (and spotted many references to the milestone) I've got the rhetorical question. But now I'm completely stuck!
"each of four answers describes a pair of others etc....."
I've just no idea how to progress
Any help gratefully appreciated!
Thanks in advance
11a. Nimrod's = Nimrod has = I've (he being the setter speaking). So you reverse (get back) alternations (intermezzi) of 'on' and 'Ive' to get envoi which means concluding section.
4d. MI6 = spies. Replace i (one) with ad(vertisement) = bill to get spades = spayads = obsolete word for deer (old dear, so to speak).