The actor will narrate a reading of the play on the day the Chilcot Inquiry is published
Further casting has been announced for Stuff Happens, which returns to The National for a one-off reading in July.
Bill Nighy will narrate the play, which explores the process leading up to the Iraq War.
Original cast members Adjoa Andoh, Isla Blair, Raad Rawi, and Iain Mitchell will return.
Also joining the cast is Tom Colley, Anton Lesser, Nicholas Woodeson, Simon Paisley Day and Sirine Saba.
Earlier this month, it was announced that playwright David Hare would direct the reading, and Alex Jennings will reprise his role as George W. Bush, which he played in the original 2004 run at the National Theatre.
On bringing the play back for this special reading, Hare said: "Twelve years later, when the inquiry into those events is to be published, it seems appropriate to mark the event by presenting the play which first laid out the diplomatic process leading to the most controversial foreign policy decision of my lifetime."
Stuff Happens will run on 6 July at the Lyttelton Theatre.