[6] At the 2003 Island Games in Guernsey, Walker won the silver in men's individual triathlon[7] and alongside Harvey Gurry and Anthony Perera finished 6th in the team event.

[8] In November 2004, Walker underwent spinal surgery (an L5-S1 diskectomy) which caused permanent nerve damage to his right calf muscle.

[15] In May 2011, Walker competed in the 2011 Ironman Lanzarote in Puerto del Carmen finishing 36th out of 299 in the male 40–44 age division and 173rd of 1469 overall in a time of 10:50:50.

[17] The following year, Walker first competed in the Ironman European Championship in Frankfurt, Germany finishing 4th out of 502 in the male 45–49 age division and 134th of 2885 overall in a personal best time of 9:36:07.

[20] The 2013 Games also saw Walker contest the triathlon where he finished in 4th place in the individual event with a time 2:03:36 and won gold in the team event with Derek Barbara, Mark Francis, Mark Garcia, Andrew Gordon, Edgar Harper, Sigurd Haveland, Robert Matto, Richard Muscat and Sean Randall.

At the 2015 ITU World Championships in Chicago Walker won Bronze in the Sprint Distance event in the 45 - 49 age group with a time of 1:04:48 [24] and finished 5th in the Standard Distance event in the 45 - 49 age group in a time of 1:50:33 [25] Walker grew up in the United Kingdom and initially moved to Gibraltar for work in the early 1990s.