Sidney was killed in action on 3 Sep 1916 having initially being listed as "missing/death presumed". The war diary for the day is transcribed below and Sidney died during the events described therein:-

Trenches between Falfemont Farm and Wedgewood 3.9.16: A general attack takes place against the Germans on the line HIGH WOOD - GUINCHY - GUILLEMONT - WEDGE WOOD - LE FOREST. French army on the right then in sequence to the left XIV Corps & XV Corps. Objectives for 13 Infantry Bde (a) the capture of FALFEMONT FARM and main line from about 400 yards to right. This attack to be carried out previous to the main attack as the possession of the Farm leaves the French left open to enfilade fire. The capture of the German main line trenches from the left of the Farm to & including WEDGE WOOD.  These attacks to be carried out by 2/KOSB's +14/R War Reg.At 9.00m the 2/KOSG advanced to the attack very gallantly and in splendid order. They were lost to sight over the ridge and from that moment until about 5pm the situation at the Farm remained obscure as no message came back from 2/KOSB.   At 12.10pm in conjunction with the 95 Bde on the left C Coy attacked the 1st objective viz the gun-pits position in the valley running S.W from WEDGE WOOD. This attack under M/G fire from both FALFEMONT FM& the gun-pits did not succeed until 1.40pm. At 12.50pm A & B Coys attacked the 2nd objective viz the enemies trenches from left edge of Farm to left of Wedge Wood with 95th Bde on the left. As it transpired the 2/KOSB had failed in their attack on the Farm. The 14/R War Reg has therefore to advance with with their right open to the concentrated fire from machine guns & rifle fire of FALFEMONT FM. Under these conditions the impossible was being asked. Both Coys advanced very gallantly and in splendid spirit but at once coming under very heavy M/G fire and losing heavily they began to with away. A Coy on the right bore the full brunt and soon dwindled away to a few remnants which however continued to advance in the most undaunted manner. B Coy on the left suffered almost as severly but struggling on managed to occupy and hold the front trench of the position just S of WEDGE WOOD. In conclusion I would say that the behaviour of the Battalion was, throughout magnificent and that it was by no fault of theirs that the attack failed.  

Capt A. Addenbrook and 2/Lt H Barrow  displayed splendid push and bravery during the attack on the gun-pits position.   I would also like to bear independent testimony to the splendidly fearless manner in which the 12/Gloucesters and 1/D.C.L.I's - 95th Bde advanced on our left and captured their objectives despite heavy losses. No sight could have been finer that these splendid Corps advancing at the walk as if on parade under a particularly violent artillery fire.   Battalion operation orders (Appendix No 1) and report on the attack (App No 2) are attached herewith. For the 5th Divisional Cmdrs speech to 13th Bde see under date 8-9-1916. Total casualties during the operations are: Officers killed 2; wounded 6 including Capt A Addenbrook. Other ranks killed or missing 141, wounded 152. Total 193. END