I've always had mixed feelings about stunt casting, but if you're gonna go that route, you might as well get Tom Hardy.
The one-man movie Locke works mostly because he's the guy doing the acting and reacting convincingly for 85 minutes straight (a good script doesn't hurt). Other voices materialize on the soundtrack, but Hardy's Locke is the only character on screen. Furthermore, twin actors can be hard to come by, so Hardy as the Kray twins represents a crazy idea that just might work—much as it did in David Cronenberg's Dead Ringers* with Jeremy Irons and Jim Jarmusch's "Cousins" with Cate Blanchett (from Coffee and Cigarettes).
* Irons may not have a twin, but Law & Order actress Jill Hennessy appears in the film with her identical twin sister, Jacqueline Hennessy, a journalist by trade.
Hungarian-born director Peter Medak previously directed brothers Gary and Martin Kemp in his stylish biopic The Krays, but it didn't make much of an impact in the US, where people are less familiar with the press-friendly British gangsters (same goes for Michael Caton-Jones's Scandal, which depicted the Profumo Affair).
Since that time, Medak has spent most of his time directing TV shows, like Carnivàle and Hannibal, while the Kemps returned to Spandau Ballet. Despite that soft-rock pedigree, they're actually pretty good at playing smooth-looking hard men, but Hardy definitely looks tougher. And buffer. So yeah: sign me up.
The Hardy film has a promising pedigree: Oscar-winning writer-director Brian Helgeland (L.A. Confidential), will be adapting the script from John Pearson's The Profession of Violence, and the supporting cast includes Emily Browning, David Thewlis, and Christopher Eccleston. A release is scheduled for 2015.