Helen Mirren will play Queen Elizabeth II in a film that delves into the strained relationship between Buckingham Palace and 10, Downing Street after Princess Diana's death on August 31, 1997.

The Guardian reported on Monday that the film -- which will be directed by Stephen Frears (My Beautiful Laundrette, Dirty Pretty Things) -- will focus on the week after Diana's death.

Tentatively titled The Queen, the director hopes Mirren's casting will make the film more appealing to audiences abroad.

Mirren -- one of the finest British actresses -- has acted in critically acclaimed films like Calendar Girls, Gosford Park, The Madness of King George and Excalibur.

Michael Sheen, who played British Prime Minister Tony Blair in Channel 4's The Deal, a television drama about the alleged pact made by Blair and Chancellor of the Exchequer Gordon Brown over the Labour party leadership, will once again play Blair.