Steve Hallam, McLaren's head of race operations, is to leave the team at the end of this year to move to NASCAR, autosport.com can reveal.
Hallam joined McLaren in 1990 after almost a decade at Lotus, where he race engineered for Nigel Mansell and Ayrton Senna.
Having helped engineer Mika Hakkinen to world title success with McLaren in 1998 and 1999, Hallam moved to a more senior role within the team's race engineering department.
McLaren F1 CEO Martin Whitmarsh has paid tribute to Hallam's contribution to the team.
"Since joining us in 1990, Steve has become a senior member of our track operations team, doing a fantastic job," explained Whitmarsh.
"He informed us of his decision to leave some time ago but, since he is totally professional, it goes without saying that we are entirely comfortable with his continuing his work with us until the end of the season.
"Next year we will all miss him greatly, but we nonetheless wish him all the very best in his new adventure."
Hallam is to take up a senior position in the NASCAR Sprint Cup Series.