Born in Southampton, England, Willis studied mechanical engineering at the famous Cambridge University before getting a job as researcher at the National Physical Laboratory in Teddington, Middlesex. Teddington is the facility which McLaren uses for its windtunnel testing work but Willis was not involved with that, as he began working with the fluid dynamics of water rather than air. There are many similarities between water and air flow and hydrodynamics has even been used by some F1 teams in the past. The water tunnels at Teddington are among the most famous in the world, although much of the work they do is for secret British defence projects. Willis also found time to become a doctor of hydrodynamic engineering at Exeter University.In 1987 he was approached to join the design team of the British America's Cup challenge and he spent the next three years designing and developing hull and keel designs for the team in preparation for the competition in San Diego. In this role he became heavily involved in the new science of computational fluid dynamics, using computers to simulate fluid flow. This is a much cheaper and faster way to develop shapes than using traditional wind and water tunnels.At the end of 1990 he was hired by Leyton House Racing and became the first engineer to use computational fluid dynamics in F1 but the team was in a slide and he moved on to Williams where he continued to develop computational fluid dynamics methods and became increasingly involved with aerodynamic research alongside Adrian Newey and Egbahl Hamidy.The 1997 season brought Willis unexpectedly into the spotlight with the departure from Williams of both Newey and Hamidy in the space of just a few months. He was appointed chief aerodynamicist at Williams andworked with chief designer Gavin Fisher on all the cars until he was asked to join BAR at the start of 2002. As technical director at Brackley Willis rebuilt the design staff and then headed the design team for the BAR 005.