The son of a veterinairy surgeon, Caldwell was six when his family emigrated from Britain to New Zealand. His brother Bill was keen on racing and the young Alastair started working as a mechanic, helping to prepare his brother's racing cars in his spare time. In 1965 however disaster struck. Bill was killed in an accident at Teretonga Park. Caldwell spent a year wondering what to do and then headed for England, intent on following a career in motor racing. Like many New Zealanders who followed the same path, he arrived at the McLaren team factory at Colnbrook and asked for a job and was taken on as a fabricator. He quickly became a mechanic and ultimately became Bruce McLaren's mechanic in F1. After McLaren's death in 1970 Caldwell played an important role in keeping the team together and was soon appointed team manager. In this role he oversaw Emerson Fittipaldi's 1974 World Championship and James Hunt's title in 1976. He moved to Brabham at the end of 1977 to be team manager there but left the team in the middle of 1981 (Nelson Piquet's title year) and was then taken on by ATS to replace Jo Ramirez. A few months later he moved on to Fittipaldi Automotive where the departure of Peter Warr had opened up a job, but that relationship lasted just a few weeks before he went back to ATS. A year later he dropped from the F1 scene.