Inspired by the exploits of Jim Clark in the early 1960s Hallam was educated at Merchant Taylors School in Formby, Lancashire, before winning a place on the famous automotive engineering course at Loughborough University. His course included a six month spell of work experience at Aston Martin in Newport Pagnell and after graduation he joined the company as the development engineer. Aston Martin was still a very small company in those days and for the next seven years Hallam was involved in the development of some famous Aston Martin models.He raced in his spare time, buying a Centaur Clubmans car and modifying it extensively. He concluded that if the opportunity arose he would try to get into racing. Eventually he saw an advertisement in an engineering journal and, amid much secrecy, found himself being offered a job by Lotus boss Colin Chapman. He joined the team at the start of 1982 and for the next three years was race engineer to Nigel Mansell. When Mansell moved to Williams, Hallam was given the job of looking after Ayrton Senna. The relationship resulted in 16 pole positions and six wins before Senna went to McLaren and Hallam found himself working with Nelson Piquet in 1988 and 1989.Team Lotus was sliding backwards in F1 and after a year with Derek Warwick in 1990 Hallam was asked by Neil Oatley to join McLaren where he became Gerhard Berger's engineer in 1991 and 1992, collecting three wins. After a poor year with Michael Andretti he worked with Mika Hakkinen in 1994 and then, after brief periods with Martin Brundle, Nigel Mansell and Mark Blundell, found himself back with Hakkinen in 1996 and was soon in charge of all race engineering at McLaren.