Walker's first
marathon was in 2000 when he entered
Sydney’s Host City Marathon, a trial event prior to the
2000 Summer Olympics. In 2007, he claimed his first marathon title by winning the
Melbourne Marathon in a time of 2:19:16. During this period he was coached by
Lee Troop. In 2010, the
Gold Coast Marathon simultaneously decided the men's and women's
Australian Marathon Champions. As the first Australian athlete to finish, Walker thus claimed the title of Australian Marathon Champion. In 2014, the Gold Coast Marathon again served as the Australian Marathon Championship, and Walker was once more the first Australian home, in 11th place overall, to take the title. From 2008 to 2017, the
Oceania Marathon and Half Marathon Championships were also decided at the Gold Coast Marathon, with Walker claiming a top three position in the Oceania marathon championship for eight consecutive years from 2008. At the 2010 Melbourne Marathon, Walker completed a personal best marathon time of 2:18:01, at the age of 40. This set a race record for the men's 40–44 age group. Walker has also placed first in the
Auckland Marathon (2012) and
Canberra Marathon (2011, 2013, 2015 and 2016). Walker has participated in a number of
ultramarathon events, including the
Kepler Challenge. In 2012, Walker was the first solo runner home in the inaugural Surf Coast Century, a 100 km ultramarathon set around
Anglesea, Victoria. He has also competed in the
Duathlon World Championships and the
Ironman Australia event in Port Macquarie. ==References==