Willis joined the Milton Keynes based team back in 2007, after previously working for Japanese manufacturer Honda as aerodynamicist and technical director. During his Formula One career, he also worked for Williams F1 team and Lleyton House team (back in the 1990s).
It was at Lleyton House that he met future colleague Adrian Newey, with whom he started working on a new project at Red Bull two years ago (after previously working side by side for Williams, back in the mid-to-late 90s). In his first year with Red Bull, the team became a consistent point finisher in the series, after which the low-performance Renault engines of 2008 caused RBR to take a fall in the constructors' classification.
This year, the Milton Keynes team was clearly the second best team in the championship, even if some might suggest Red Bull have already topped Brawn GP in terms of on-track performance. Red Bull recorded two 1-2 finishes this season, both led by Sebastian Vettel, in China and Great Britain.
The team is now expected to give further clarification for Willis' departure, while also announcing a new technical director for the remainder of the season.