On night duty for two hours 1 - 3 AM. Up at 5. Stand to until 7 AM. Sent to Bde. H. Q. Arras at 9 o'clock. Error made in order, so came back to cave. R. C. service at 9, but no Protestant. Slept for an hour, in forenoon. Relieved by London Scots at 10 PM marched Bn out of cave by tunnel and sewer to Lewis Barracks and to N. E. Side of Arras. Very tiresome trip and so slow. Took 2 ¾ hours to go about 2 miles underground.