[4] At the combined public schools sport meeting held at the Melbourne Cricket Ground on 3 May 1906, Walker tied for first place in the Under-14 High jump, with a leap of 4 ft 5in (135 cm), which broke the existing record.

[14] He enlisted in the First AIF on 4 January 1915, and left Australia on 14 April 1915 on the HMAT Wiltshire.

[15] He served with the 8th Australian Infantry Battalion in Gallipoli and France, and was promoted to Sergeant on 2 May 1916.

[18] He is commemorated at the Villers–Bretonneux Australian National Memorial, and at the Melbourne Grammar School Honour Roll.

[19] On Monday, 28 August 1916, the Dandenong Town Hall flag was flown at half mast;[20] and, on Saturday, 2 September 1916, in their match against the Navy Office, the Dendenong Patriotics players wore armbands out of respect for the late Sergeant Jack Walker, recently killed in France.