Robertson best results include winning gold at the 2004 European Championships in Geneva, and a silver medal at the 2004 Olympic Games, both partnering Gail Emms in the mixed doubles.

Robertson competed in badminton at the 2004 Summer Olympics in men's doubles with partner Anthony Clark.

In the quarterfinals, Robertson and Emms beat Chen Qiqiu and Zhao Tingting of China 15–8, 17–15 to advance to the semifinals.

In the final, they lost to Chinese pair Zhang Jun and Gao Ling 1–15, 15–12, 12–15 to finish with the silver medal.

The 2006 Commonwealth Games brought Robertson a silver in the team event and a gold in the mixed doubles with Emms.

Robertson was part of the English team forced to withdraw from the 2009 World Championships held in Hyderabad, India because of a terrorist threat.