Percy is listed as being killed in action 25 Sep 1915, the first day of the Battle of Loos. The Battalion's Commanding Officer's diary entry for the day is transcribed below.

Commanding Officers (Colonel Eden's) Diary:

September 25th: Very early in the morning we were told that zero hour was fixed for 6 a.m., and that, for 10 minutes previous to that, gas (officially called "Accessory Cylinders") and smoke would be discharged from our front trenches. The 5th Brigade was to attack half an hour earlier than the attacks southwards. In this neighbourhood, at the above hour, the air was practically motionless, with the result that the gas hung very considerably, and in our part of the line did more harm to our men than to the enemy, who, in only very few cases, were found to have suffered from the effects. A Company got across the 200 yards well, and soon gained a footing in a good length of the Huns' front trench, some parties reaching the support line or even farther. But the enemy, by bringing up reinforcements, gradually made our hold on the captured trenches more and more precarious, and in the end, by 11a.m., A Company was back again in our own front line.

Between 8 and 9 a.m. Hughes had taken out a platoon of C Company to assist A, but could make no headway across No Man's Land under the enemy's artillery fire, which by then was pretty severe everywhere. D Company, advancing from the neighbourhood of the Warren, met with even less success, for opposite them the gas hung in one or two places, and even blew back into our own trenches. Moreover, in front of the company were some strongly defended craters, and the enemy's machine-guns were ready to meet an advance. Newton-King, with a couple of sections, attempted to outflank these par­ticular craters ; but, after rounding one corner of them, nearly the whole party was destroyed. Many of D Company though wearing smoke helmets, felt the effects of our gas, but kept their position in spite of it.

The other battalions of the Brigade fared no better. The wind was so perverse with the Glasgow Highlanders that they never even left their trenches, whilst in the case of the 2nd H.L.I, at Duck's Bill and the 1st Queen's in between, although two companies of each reached the enemy's line, they were also driven back. Vidal made a brave effort to take a couple of our machine-guns across, but perished in the attempt. Altogether it was a most unsatisfactory affair, and the only consolation that I could derive from it was the knowledge of the fact that Owen's company was the last to leave the enemy's lines. The other two brigades of the Division had no luck either, but farther south the Army's effort met with considerable success Between 6 and 11 a.m. our trenches were pretty heavily bombarded by whiz-bangs, while still heavier shells were directed on the neighbourhood of the church. The remainder of the day and night was quiet. The 5th Brigade had been told not to press their attack con­tinuously should the first results be fruitless. A section of the 5th Field Company R.E. was in readiness to assist should the attack be successful.

A working party of 100 men of the 7th King's (Liverpool) Regi­ment was employed in digging out a communication trench, but the work did not proceed very far. In one part of the line a party similarly employed very greatly impeded the advance of reinforce­ments on this line of slight cover. 

Casualties :--
Killed 3 officers and 33 men
Died of Wounds (the next day) 1 officer
Wounded 5 officers and 124 man
Missing 1 officer and 60 men (all presumed killed) Total casualties, 236 officers and men.

The above courtesy of The Light Bobs website