I literally could only keep my sanity by working a region at a time (see below, the outer frame was done first, then the red uniforms with (annoying black hats), onto the horses whilst muttering under my breath):
Horse's heads complete I moved onto the bodies and legs (see below, the study in white and cream was a different form of madness, at least the legs helped me segment the very challenging brown earth section):
The finished masterpiece, I do think it looks impressive (see below, shown with three missing chinks - due to its missing parts and an element f wear and tear I think its active days as a jigsaw are over. Rather than chucking it I plan to slide it onto a board, PVA it into place - then fill in the remaining two spaces):
Footnote 1: I was mighty glad (aka understatement) to have finished it but slightly saddened about the three missing pieces, which later reduced to "two" when I discovered one in an unusual place. Either I picked it up already "short" from the Charity Shop or managed to lose two with all the holiday travels (I used one of those clever jigsaw zipped portfolio folders to transport it). I also do have a small number of 28mm Napoleonic Scots Greys I was thinking of painting up (a couple of sprues rather than the whole Warlord Box).