Born in Glasgow Callum was inspired to take up track cycling in 2004, when fellow Scotsman Sir Chris Hoy won gold in the kilo at the Olympic Games in Athens. Four years later after moving to Edinburgh and having access to a local track (Meadowbank), Callum smashed the national 200m record for his age category for which Sir Chris presented him with the inaugural Chris Hoy Trophy in recognition for this achievement.
Callum joined British Cycling’s Academy Programme in 2010, having progressed through the Talent Team and Olympic Development Programme.
He was selected to represent Scotland at the 2010 Commonwealth Games in Delhi, where he came fourth in the team sprint. In 2011, Callum represented Great Britain at the under-23 European track cycling championships in Portugal where he brought home two medals - a silver in the team sprint and a bronze in the sprint.
In April 2013, Callum progressed onto the Podium programme and he won his first world cup medal at the third round of the 2013/14 series when he, along with Lewis Oliva and John Paul took the bronze medal in the team sprint.
Fresh from winning four titles at the National Track Championships in September, Callum was crowned the European champion in the kilo event in 2014. A couple of weeks later, Callum won his first gold medal at world cup level, winning the team sprint event with current Olympic champions Jason Kenny and Phil Hindes in Mexico.