Over and over again the wounded swore to God that they had been shelled by our own guns. The Londoners said so from High Wood. The Australians said so from Mouquet Farm. The Scots said so from Longueval! They said: “Why the hell do we get murdered by British gunners? What’s the good of fighting if we’re slaughtered by our own side?”

In some cases they were mistaken. It was enfilade fire from German batteries. But often it happened according to the way of that telephone conversation in the tent by Bronfay Farm.

The difference between British soldiers and German soldiers crawling over shell-craters or crouching below the banks of a sunken road was no more than the difference between two tribes of ants. Our flying scouts, however low they flew, risking the Archies and machine-gun bullets, often mistook khaki for field gray, and came back with false reports which led to tragedy.