[4] Having previously played football for Harrow School, Sumner represented Oxford University, where he was described as "most effective", winning praise for his "fine runs", "vigour" and willingness to work hard for the team.
[6] In the final, played at Lillie Bridge on 29 March 1873, the university met the defending champions, Wanderers who, under the original rules of the competition, were exempt from the earlier rounds.
[8] In a desperate attempt to secure an equalising goal, Oxford took the unusual step of dispensing with the use of a goalkeeper and moved Andrew Leach upfield to play as a forward.
[4] Following his graduation in 1875, Sumner worked as a schoolmaster and in 1881 he was teaching at a preparatory school run by Alfred Hyde Harrison at The Lodge, Dunchurch, near Rugby, Warwickshire.
Soon afterward the couple moved to Yampa, Colorado and had two children: Mary Beatrice (1891–1972; married Clarence Rufus Blankenship) and John Robert Carew Sumner (1892–1961).