Beginning in 1958 with an Lotus VI in the 1172 championship, in 1959, Hart teamed up with Len Terry to drive his Terrier Mk2 in the championship and won the Chapman Trophy. In 1960, he drove Terry's front-engined Formula Junior Terrier Mk4 and developed a downdraught head for the Ford Anglia engine powering the car. At Oulton Park in October 1960, Hart had a bad crash with the car, which led to Terry designing the Mk4 series 2, which Hart drove in 1961. The rear-engined cars were now the state of the art and Hart had only limited success with the car. Hart enjoyed a successful career as a driver in various single-seater formulae. He competed in Formula Junior and Formula Three, then graduated to Formula Two with the works Lotus Formula Two team run by Ron Harris. He competed in a handful of non-championship Formula One races using Formula Two cars and in 1967, he qualified for the German Grand Prix at the Nürburgring in a Protos-Cosworth.