The poets Edward Thomas, R.E. Vernède, William Maunsell Scanlan, MC, MM and Walter Lightowler Wilkinson were killed on the first day of the Battle of Arras, which was Easter Monday, 9th April 1917. My Great Uncle was also killed on that day during that battle. The poet William Henry Littlejohn was mortally wounded on 9th April 1917 and died the following day.
With thanks to Paul Johnson for finding the image entitled "Zero, 9 April 1917" by Major C.J.B. Way, RAMC, which is taken from the book "The Golden Horseshoe".