Mann was born in London in 1938, and attended engineering school in Westminster. His automotive design career started with the bus and coach building firm Duple, followed by a short time working in the U.S. with Loewy Consultancy. After a brief spell of National Service back in the UK, Mann worked for Commer, and then for Ford.
Cars on which Mann was involved at Ford included the first Escort and the Capri. His boss at Ford, Roy Haynes, persuaded Mann to go with him when, in 1967, he moved to BMC to lead the design studio at Cowley.
Mann worked alongside Haynes on the BMC Marina project and, when the design department they were working in was relocated to Longbridge, Haynes left the company, leaving Mann to lead the design team for, what was by then, British Leyland (BL).
Mann took over the Allegro project, and then worked on the Diablo project, which became the Princess. That was followed by the work for which he is most famous, the Triumph TR7. His final project with BL was the Metro, after which he left and went freelance. In that capacity he worked for MG Rover on the MG "Z" series (the ZR, ZS, and the ZT). He was also a design consultant for BMW in the mid 1980s, for which he was required to submit plans for a new corporate style and, in particular, to work on bonnet and boot shut lines and lights. According to Mann, "BMW shut lines were all over the place at that time". He proposed several designs to the BMW board, including the double headlight design, very reminiscent of the Princess, which is still seen on BMW cars today.
Later, Mann was involved in independent design consultancy in the automotive sector, and lectured in design at Coventry University.
- "Harris Mann Interview". Classic Cars Magazine: 70–73. January 2005.
- "The Designer: Harris Man". Classic Car Weekly. December 2004.
- "The Designer: Harris Mann". Retrieved 8 February 2006.