Born in the suburbs of London in 1946, Field was the son of an innkeeper and he spent his early life moving from pub to pub until the family settled in the Portsmouth area.It was in there that Greg became an apprentice mechanic working at a BMW dealership in the town of Havant. This led to him meeting the local racing hero David Purley, who ran the Lec team, which was named after his family's refrigeration business. In 1973 Field joined Lec to help team boss Mike Earle to run a car for Purley in the British Formula Atlantic series.The following year Lec ran a pair of cars in the European Formula 2 Championship for Purley and Austrian Dieter Quester, and in 1975 and 1976 ran a Chevron chassis in European Formula 5000 series. Purley became the 1976 European Champion. The team - which had only five crew and a part-time fabricator - began to build its own Lec F1 car as well as running the F5000. An exhausted Field decided he could go on no longer and joined Ron Dennis's Formula 2 team, which was running a Ralt-BMW for Brazilian driver Ingo Hoffmann. He continued with Dennis in 1978 running Eddie Cheever's BMW Junior team car.At the end of 1978, however, Mike Earle asked Field to be his partner in a new racing team which would be called Onyx. They built an F2 car but this was not a success and so in 1980 they switched to March chassis and ran motorcycle ace Johnny Cecotto with some success. When Cecotto went to the works March team Onyx took on wealthy Italian youngster Riccardo Paletti.In 1982 Onyx decided to get back into F1 and entered a private March for Spaniard Emilio de Villota. He failed to qualify for all five races which the team had entered.Wanting more time at home, Field sold his shares in Onyx to Jo Chamberlain and went to work as a home-based mechanic for Benetton. Onyx finally got into F1 in 1989 and Field rejoined for a brief period as team manager before leaving F1 to work with Vern Schuppan's sportscar team in Japan. He went briefly to Team Lotus in 1991 and then to Brabham, arriving just in time for the team to close down. While looking for a new job Greg set up two businesses to exploit aspects of F1 which were not catered for: one (Grand Prix Badges) sells badge pins for various teams while the other (Moving Cars International) transports show cars around the world for the F1 teams.It was while delivering a show car to Benetton at the end of 1993 that he was asked by team manager Joan Villadelprat if he would like to become Benetton's team coordinator. He took the job and stayed at Enstone until he was headhunted by British American Racing in May 1998. Field oversaw the fitting out of the new BAR factory and the establishment of the race team but when the team failed to deliver results at the start of 1999 he was used as the scapegoat and dumped.