William's family originated from the Carlisle area. He had been born there, although Regimental records note his place of birth as Edgeley. The family had moved to Stockport in the mid 1880s. The 1901 Census shows that he was the oldest of seven children. His brother and sisters were Charles (4), George (6), James (9), Elizabeth (11), Margaret (15), Roland (15). Their mother, Janet, was then aged 44. Their father, John, had died between December 1900 and February 1901, aged 44.
The Census records William, then aged 17, working as Leather Dyer in the local hatmaking industry. It would seem, from his army service number, that he left this job and joined the army as a regular soldier. He was probably still serving when war was declared in August 1914 (although he may have been a reservist who was recalled).
On 31 May, the Cheshires were at positions near Dormy House, Zillebeke (approximately two kilometres south east of Ypres (now Ieper). The Battalion's War Diary makes no mention of casualties for the day. It does note that the unit's Commanding Officer "visited all the trenches and that "B" Company relieved "C" Company in Rifle Pits. "C" Company sends two platoons to "51 dugouts" and two platoons to new position in Maple Wood". William has no known grave, possibly suggesting he was killed by a direct hit from an artillery shell.
Nearly two years later, William's parents would receive more bad news. Charlie McClellan was killed in action on 10 February 1917. A letter from his officer suggests that a third brother was also serving.