Service Record shows that William was promoted to  the rank of Sergeant, 2nd August 1917. The Official Roll of Honour confirms his rank. 

Records do not show his cause of death, but do show that he suffered from Asthma from childhood, which prevented his service overseas, and was frequently hospitalised with symptoms.

"The military funerals of Gunner Francis James Nicholl and of Private William John Will, both of whom died at the Christchurch Hospital on Sunday, left that institution to-day, at 2 p.m., en route for the Linwood Cemetery. The casket containing the body of Gunner Nicholl, who had served on the permanent artillery staff at Ripa Island, was borne on a gun carriage, which was followed by a motor hearse bearing the body of Private Will. Private Will had served on the dental staff at Tauherenikau Camp. The two firing parties were supplied from the local permanent artillery force, whilst the pall-bearers were artillery men and medical corps men. Both coffins were draped with Union Jacks. In the case of Gunner Nicholl, the last rites at tho graveside were performed by the Rev C. A. Fraer (Church of England). Private Will, who was a Roman Catholic, waa buried with the full rites of the Roman Catholic Church. At the conclusion of each service the firing party fired three volleys, and the “Last Post” was sounded." [Star (Christchurch), Issue 12324, 22 May 1918, Page 6]