Jim Broadbent stars in 'Longford', premiering Saturday on HBO.

Jim Broadbent vanishes so completely into his film roles that he seems less a character actor than a phantom.

Watch his recent gallery of performances - as testy librettist W.S. Gilbert in Topsy-Turvy, manic impresario Harold Zidler in Moulin Rouge, and his Oscar-winning turn as John Bayley, the long-suffering husband of Alzheimer's-stricken writer Iris Murdoch (Judi Dench) in Iris - and you may find yourself doubting that you are watching the same actor in all three roles.

In fact, it's a little tricky to get a read on Broadbent himself even when he's sitting just a few feet away from you, his face and shoulders backlit by sunlight streaming through the windows of a California hotel room, where he has come to talk about his new HBO movie, Longford.

Fact-based drama

Written by Peter Morgan (The Queen), the fact-based drama, which premieres Saturday, February 17, stars Broadbent, 57, as Lord Longford, the eccentric and controversial British politician who put his reputation and career in jeopardy by campaigning for the release of a notorious serial killer, Myra Hindley (former Oscar nominee Samantha Morton, In America).

Set in the last three decades of his life, the movie follows Longford as he becomes increasingly driven to win parole for Hindley, who was convicted of acting with her lover, Ian Brady (Andy Serkis, Peter Jackson's Lord of the Rings movies), to murder several children in the 1960s. While the case is not very well known in the United States, it remains a hot-button topic in Broadbent's native England, he says.

"My generation, anyway, has always been aware of Lord Longford in some way, because he was quite a character on the political scene," Broadbent explains. "And the Myra Hindley story was massive and continues to be a benchmark of how serial killers are treated in the press. It's been a few years since she died, but she was always presented as archetypally wicked."

- John Crook, Zap2it