The David Tennant Treat 4 Today is a link to the Glorious 39 web page from BBC Films.
The film was set in England in 1939, where in spite of the prospect of World War II being very close, the Keyes family of the English aristocracy, tries to uphold its traditional way of life. Anne (played by Romola Garai) sees her life unravel when she stumbles upon secret recordings that could shake the family to its foundations.
Stephen Poliakoff wrote and directed the film which was released in 2009.
David Tennant plays the role of Hector Haldane who is a Member of Parliament .
This link is a wonderful source for this film. The link below has production images, a set report, a synopsis of the film and an interview with some of the cast from the premiere.
BBC Film Glorious 39