At the 2005 World Championships in Gifu, Japan, the men's quad narrowly failed to reach the final.

[3] In 2006, Campbell switched to competing in the men's heavyweight single, and won the Munich world cup regatta ahead of Olaf Tufte.

He also finished second in Lucerne, behind Mahé Drysdale, and fourth in Poznań, to win the overall world cup standings.

Campbell competed in the 2008 Olympics in Beijing where he participated in the Men's Single Scull; he led up to 1000m, where he was overtaken by Olaf Tufte and finished fifth.

Prior to the games, he had picked up a virus that required knee surgery, which left him on crutches for three weeks in June 2008.