About the latter point, Durran said, "The main impact of that was [the necessity of keeping tabs on] miniscule [sic] details of continuity...and there was an impact on the number of duplicates that you need, because if you have to go back to the beginning of the take every time, you may need to change. It had a huge effect in the amount of work it was, because every day, you’d have everybody out. You’d have the whole run of the trench, the crowd and all those things." Amazingly, "We had breakdown people that were doing mud for the whole shoot. They’d come to set and redo the mud, and they’d be mud matching, knowing which take they were matching to. All of those things were critical, really."
In relation to the historical accuracy of the World War I uniforms, Durran said the following (a quote I have included in full because the final part is so interesting that, upon reading it, I said out loud, alone in a room, "Oh my god, that is so fascinating. Holy crap."):
"We had a whole wall in our office of pictures, archived photographs from books. We took stills from Peter Jackson’s documentary [They Shall Not Grow Old], and looked at them constantly, through the whole prep period.
We looked for details, and different ways in which people wore a uniform — how they customized it, what they wore with it. Different jobs in the trenches that meant that people wore different things, whether they were waders [boots] or spades, all these different things. There was actually an endless number of details evident in these photographs, so that was our object.
David Crossman, who co-designed it with me, knows so much about uniform, and about the detail and the history of it. Because he’d done the period before, he knew that people generally used World War II helmets for World War I, because there’s less World War I helmets around. He put an original World War I helmet onto a modern head, and worked out that the scale was wrong, because modern heads were bigger than World War I heads. So, we had a helmet which was 100% the size of an original World War I helmet. Then, we had 106, 108. We went to extreme detail to try and represent the scale that a period helmet would have on a modern head, really trying to make it as accurate as possible."