Chief operations engineer Mark Gillan has left the Williams team in order to "to spend more time with his family".
The Ulsterman, who previously worked at McLaren, Jaguar/Red Bull and Toyota Motorsport, was lured to the Grove-based squad in September 2011 as part of the team's hopes to arrest their disastrous campaign that season as they scored just five points and finished ninth in the standings.
Gillan and company managed to turn the team's fortunes around this year with Pastor Maldonado winning the Spanish Grand Prix to end their eight-year wait for a race victory.
Despite the team's resurgence, Gillan has decided to step down and he is officially on "gardening leave" until the end of December.
According to reports, race engineer Tom McCullough and strategy engineer Mark Barnett have also left the team with the former joining Sauber and Barnett heading to Force India.
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