He said: "I was one of the lucky ones. I returned from Afghanistan unscathed. Many of my friends and colleagues did not.
"Amongst those who died was my great friend Lt Paul Mervis and completing this challenge is the least I can do to mark his memory and help those who paid such a dear price.
"At one stage during the summer there seemed to be an awful incident almost every day. In one bomb blast we lost five men.
"I hope my effort will go some way to helping those with horrific injuries readjust to normal life."