They are Belinda Richards and Bill Thomas.
Belinda Richards headed Deloitte's merger integration and separation advisory services business until 2010. She is also a non-executive director of Grainger and of Resolution.
Bill Thomas was a senior vice president of Hewlett-Packard until 2009. Before this, he was with Electronic Data Systems (EDS). He is also a non-executive director of Xchanging and GFI Software.
After nearly eight years, Mike Donovan will be retiring from the board on 1 October 2013.
Chairman Steve Marshall said: "Belinda brings a wealth of experience that encompasses strategy, change management and managing operational delivery across a range of sectors. Bill brings a track record of growing successful businesses and considerable strategic and international experience from within the professional services arena."