1. The attack on LONG TRENCH in which the 23rd ARMY BRIGADE is co-operating will take place at 4.45 am on 17th inst & not 5 a.m.
2. The TEST S.O.S. as laid down in my Sa/28 will take place to-night. The signal will be 1 GREEN LIGHT, & not the S.O.S. signal.
Officers at Brigade O.P. & Liaison will report to this office on seeing the light which will be sent up from INF BRIGADE H.Q. (H.23.b.3.2.)
On completion of test each battery will report time of seeing the light & firing the round.
V.C. Ritchie Lt. R.F.A.