In addition to their general board responsibilities, Mr Holaday will serve on the board’s audit committee and Mr Knudson will serve on the compensation committee.

Mr Holaday headed the private markets group of UBS Asset Management and its predecessor entities for 15 years prior to his retirement in 2001.

Mr Knudson is president of Tom Knudson Interests, which provides consulting services in energy, sustainable development and leadership. He also is the chairman of Bristow Group and a director of Natco Group. Mr Knudson retired in 2004 from ConocoPhillips.

Harry Pearce, chairman of MDU Resources, said: Bart and Tom bring a wealth of valuable senior leadership experience that will help guide the continued growth of our company. They are widely respected for their expertise in oil and natural gas development, which is one of our core businesses. In addition, Bart’s experience with equity investing, and Tom’s knowledge of sustainable business development, will enhance the existing knowledge of our board.