Nothing is known of Percy's life, except that regimental records published after the War indicate he had been born within the parish of St Thomas' Church, Stockport and was living in the town when he joined the army. He enlisted at Manchester into the first of the "Manchester Pals" Battalions - the 16th. The City Battalions Book of Honour confirms that he was a member of 1st Platoon, "A" Company confirming he was amongst the first 50 or so men to join the Pals on the first day of recruitment. Although it is not known what he did for a living, it can be said with certainty that the men joining on the first day were all employees of the city centre's major firms.
At some point, Percy was probably injured or away from his Battalion due to illness for a considerable time. When he had recovered, it will have been decided that the 5th (Territorial) Battalion was more in need of replacement troops and this is when he will have been transferred.
Percy was killed during the Battle of the Selle (a river that had to be crossed to continue the final advances that would end the War). The previous day, bridging had been completed and zero hour for the advance was set for 2am on the 20th. The plan was that the Army's 126th Brigade would lead the attack and capture the first objectives. This included a position known to the British as Belle Vue farm (and now the location of Belle Vue Cemetery). 127th Brigade, which included the 5th Manchesters, would then leapfrog the 126th and continue to advance towards the hamlet of Marou about 1500 yards further on. After a pause to reorganise, they would continue and capture an important crossroads on top of a hill between Marou and Romieres.
The men of 126th Brigade secured their objectives after hard fighting and, at 7am, the 5th, 6th and 7th Manchesters took up the attack. The History of 42nd Division recalls "At the outset, the 5th Manchesters were badly knocked about by enfilading machine gun fire from the right flank, which caught the advancing waves on the bare high ground, south of Marou and west of Maison Rouge which had to be crossed. The deadliness of this enfilading fire was due to the fact that very strong enemy counter-attacks had forced the division on the right to withdraw temporarily, so the right flank of the Wigan men was in the air. The enemy was offering a stubborn resistance, infantry and machine -gunners fighting skilfully and well."
The 7th Manchesters were now brought forward from their supporting position and they formed a defensive flank on the right of the 5th. It was now possible to continue the advance for some little distance but the fire from the flanks was still too heavy to permit the assault on the objective. It was about this time that one of Percy's comrades, Albert Wilkinson, won the Victoria Cross. The Divisional History records "His company was held up in an exposed position by very heavy machine gun fire from the front and right flank. All other means of communication having failed, four runners were sent out in succession with messages asking for assistance and all four were killed before many yards had been covered. Though Wilkinson had seen the four shot down, and therefore knew how slight his chance of escape would be, he volunteered to carry the message. The distance was more than 600 yards but somehow, though scores of bullets only missed him by inches, he got through and assistance was sent."
Later in the afternoon, another Division was thrown into the attack, supported by the 5th and 6th Manchesters, and these fresh troops were able to secure all the objectives. Percy was one of 28 members of the 5th Battalion to have been killed during the day.