Callum devoted the first twelve years of his professional career to working at the Ford design studio, after which he took the post of chief designer at TWR Design. It was there that he created such iconic models as the Aston Martin DB7, Vanquish, and DB9.

In 1999, he became the head of the design department at Jaguar. It was under his leadership that the F-Type appeared — the brand's first two-door sports car since the iconic E-Type, as well as the XE, XF, and XJ sedans and the F-Pace and E-Pace crossovers. In addition, Callum was at the origins of the I-Pace — the first electric vehicle of the British brand, which in 2019 was named "Car of the Year".

"My career at Jaguar was incredible. I consider the XF one of my main achievements — a model that opened a new chapter in the transition from classic to modern design. The F-Type was the embodiment of a dream, and the I-Pace gave me the chance to create a truly innovative product," Callum shared.