Baroness Rock is presently senior adviser at public relations company Instinctif Partners, and was previously a managing partner of its predecessor communication firm College Hill Associates.
She is also, until January 2023, a member of the House of Lords Select Committee for Science and Technology.
Also since 2020, Baroness Rock has been senior independent director of international ground engineering contractor Keller Group.
Tony Quinlan, Costain’s senior independent director, said: “Having conducted an extensive search process, we are delighted to welcome Kate to the board of Costain where she will support the Group in the next stage of its transformation.
“She brings a strong understanding of the construction contracting sector, the application of innovation and technology to drive productivity enhancements, and of government.”
He added: “On behalf of the board, I would also like to thank Paul for his considerable contribution to Costain for over six years.
“He has led Costain through a period of significant change and leaves the Group in a strong position for the future. We wish Paul all the very best.”