No Raggy - you assumed the gun was fired, but there is no evidence, or clear statement that it was. I have no idea if an officer did shout, "Coooeeeeee !!! Come on boys, back to your trenches" but there is a clear statement that an officer did shout to tell the men to come down from the parapet.

"As it happens Captain Ian Colquhoun a Company Commander and the Commanding Officer of the 1st Scots Guards, Miles Barnes, were taken before a Court of Enquiry and were later Court Martialled. Barnes was acquitted and Colquhoun received a reprimand which wasn't followed up."

Care to tell us what the charges were?