Callum was born in Cambridge, UK, on November 11th 1998. Callum had his first drive in a kart just before his 7th birthday. At 12 years old he became the under 16s Formula Kart Stars British Champion and finished 3rd in the German KFJ National Championship. At 13, Callum dominated the international under 15s KFJ category, winning the WSK Masters Series, the WSK Final Cup, and was runner-up in both the WSK Euro Series and the CIK-FIA World Cup. He was nominated as the youngest ever WSK Driver of the Year in 2012. As a 15 year old, in 2014 Callum become the senior CIK-FIA European Karting Champion, he won the seniors WSK Super Master Series, and finished 4th out of 32 competitors in the CIK-FIA World Championship. Callum made an unusual debut in single-seater racing at 16, jumping straight from karting up to F3, competing in the FIA F3 European Championship for three years. In his first season he finished 12th overall, out of a grid of 35 seasoned drivers, and then finished 6th overall in 2016. In 2017, Callum took 6 wins, 11 podiums and 10 pole positions in the FIA F3 European Championship, finishing 4th overall. He rounded off his 2017 F3 campaign with a win in the FIA F3 World Cup Qualification Race at the Macau GP street circuit.