Mark Morris O’Keeffe (SN 35) ) was from Pleasant Street Ballarat but was working as a labourer in Northam, Western Australia when he enlisted on January 18th 1917. He trained at Blackboy Hill, outside Perth, with the 10th Light Horse before embarking from Fremantle on June 30th , aboard the Port Lincoln. He disembarked at Suez and served in Egypt, first with the 3rd Light Horse Ambulance Brigade before being transferred to the 3rd Australian Machine Gun Squadron. On July 5th 1918 he was hospitalised as a result of a heavy blow to his lower right side. The incident was formally investigated to determine whether his injury was accidental or self-inflicted, and it was found that while trying to remove a fly that was annoying his horse he was kicked in the side by the agitated horse. No blame was assigned to him. On July 9th 1919 he left England on the Oxfordshire to return home. He reached Fremantle on August 5th but failed to reboard and was charged with being absent without leave. He did re-embark 12 days later and reached Melbourne on August 28th. He was discharged on September 12th 1919.

His brother James was killed in action in October 1917 and his brother Frank also served in the AIF and they are honoured with trees in the Avenue.

Lucas’s Staffs Appreciation of Brave Men, the original Avenue register, records his name as Mark O'Keefe.