I'm not sure if mail was censured in WW1 but the mail certainly got there quick, see link.Interesting reading your links, Roy.
It seems remarkable that the truce took place only nine days after the German Navy bombarded Hartlepool on the morning of 16th December 1914. Over 1,000 shells were fired during the bombardment causing much devastation to the town and its people. More than 100 people were killed and in excess of 200 were injured. This attack on the British mainland had an enormous effect on the British public confirming to many people that we were fighting a nation of barbarians. One wonders if the troops in the trenches had heard about Hartlepool and if they had, then the truce was certainly remarkable.