Saw it at the cinema a few weeks ago and watched again last night. That part of the film where it slows down and turns to colour is so effectively done and expertly timed.
Another must watch is WW1's Secret Shame - Shell shock. Dan Snow's documentary looks at Shell Shock in WW1 and about mental trauma and PTSD suffered by soldiers that resonates today as it did then and how we still fail the young men we send to fight on our behalf.
Most of the comments by survivors seemed just to accept what happened as a matter of fact and some appeared to miss the'life'.
I thought the title was a bit of a mismatch, really.
"They shall not grow old" obviously refers to those who didn't come back, but the doc was from the point of view of those who did.