I wonder if you have worked out where Capt. Maurice Jacks was when he wrote:
“Being more or less conscientious I cannot tell you exactly where ‘here’ is, but if you remember where Polonius was stabbed, you will be within reasonable distance of the spot.”
Polonius was hiding behind a rich tapestry (typically hung to make a screen) when stabbed by Hamlet. Such a tapestry was called an arras.
So, our man is somewhere near the town of Arras, to the north of Albert in the region of the Somme.
Two marks if you got it right, one if you got it wrong!