William was born on 18th February 1896. He was the son of Hubert, who owned a slater company, and Margaret Wylie, of 16 Morpeth Avenue, South Shields. He was also the nephew of his namesake William Gladstone Wylie, Mayor of South Shields from 1907 - 1908, and had an older brother Hubert. He was educated at South Shields Boys' High School, through a Corporation Scholarship. When the scholarship ran out, school records show that he left "to learn farming", presumably through studying agriculture at Armstrong College. He later became a cowman on a farm in Humshaugh.
William initially served with the Northumberland Hussars as a Lance Corporal, but later moved to the Durham Light Infantry, 9th Battalion, as a Lieutenant. He was awarded the Military Cross on 18th July 1917 for conspicuous gallantry and devotion to duty when in command of a party of 200 men carrying ammunition to the front line. Though on his arrival at the position there was no dump and no guide, he eventually succeeded in obtaining and delivering his stores. He carried out his task in spite of intense shellfire, and numerous casualties amongst his party. He set a fine example of good leadership during the 27½ hours occupied by the operation.
William died while serving in France on 28th March 1918, aged 22.