The chief financial officer of Hampshire-based QinetiQ Group is set to leave to take up the same role at aerospace and defence group Cobham.
David Mellors (pictured) has been with Qinetiq since 2008 and has been "pivotal in the turnaround of the company and the strengthening of its balance sheet".
He has previously held roles at Logica, including deputy chief financial officer, chief financial officer of its international division and group financial controller, and at CMG, Rio Tinto and Price Waterhouse.
Mellors will leave QinetiQ on 31 December 2016. The search for a new chief financial officer is already underway.
Chairman Mark Elliott said: "On behalf of the board, I would like to thank David for his significant contribution to QinetiQ over the last eight years. We wish him every success in his new role."
Steve Wadey, QinetiQ chief executive, added: "The capital discipline and strong financial position established under David's leadership will underpin our future success and allow us to invest selectively in future growth.
"I would also like to thank him personally for the advice and support he has given me during my first year as CEO."