By 2003 Robertson was joined by fellow British sailor Hannah Stodel and newcomer to the sport, ice sledge hockey Paralympian Stephen Thomas, to make up a Mixed Sonar crew.

In 2003 he travelled with his teammates to Athens to take part in the IFDS World Disabled Sailing Championship, where they secured the bronze medal.

[1] Two silver medals in the 2010 and 2011 IFDS World Championships were followed by their third successive Paralympics, this time on home surf when the games came to London.

The London Paralympics ended in disappointment for Robertson and his teammates after they were deducted four points after a team bosun cleaned the port side of their keel after being authorized to inspect the craft for damage.

[5] In the run up to the 2016 Summer Paralympics in Rio, Robertson skippered his crew to a third World Championship, beating the Australian team by a single point.