Don’t lie to me. You’re not American.

Tim Roth is best known for getting shot in the stomach in Reservoir Dogs and robbing a diner in Pulp Fiction, but now he’s doing something more dangerous: using a British accent on a U.S. TV show. When the London-born Roth agreed to play “human lie detector” Dr. Cal Lightman on Fox’s new show Lie to Me, the network probably figured he would play the part as an American; he’s done U.S. accents before in many movies, including Reservoir Dogs. Instead, Roth decided that, unlike most British or Australian actors on TV, he would pronounce “can’t” as “cahnt.” Paul Meier, an English dialect coach who has worked with such actors as Jonathan Rhys Meyers (The Tudors) and Tobey Maguire, says that U.S. producers usually save British accents for “the villain’s role, or, and I don’t know which is less rewarding, the role that lends the project some cultural heft.” But if Lie to Me succeeds, Meier says it might prove that “we are approaching the point when the American prime-time viewer can accept a ‘furriner’ in the starring role.”

American producers love English actors, and English actors like the higher pay and steadier employment of a hit American series. But there’s also a long-standing feeling among U.S. entertainment executives that Americans won’t accept a hero who doesn’t sound like them, particularly on television, where even the most anti-social heroes need to have an Everyman quality. The solution is for transplanted Brits to learn how to sound American. Hugh Laurie as Dr. House is the most famous fake American in the world, but there’s also Damian Lewis on Life, Jamie Bamber on Battlestar Galactica, and Anna Friel on the recently cancelled Pushing Daisies. They’re all English, but even Englishmen can’t tell; Roth told fancast.com that “I didn’t know the guy in The Wire [Dominic West] was English. He’s that good.” Aussies like Simon Baker on The Mentalist, Rose Byrne on Damages and Yvonne Strahovski as a CIA agent on Chuck are all equally adept at disguising their accents. New Zealander Anna Paquin doesn’t have a convincing southern accent on True Blood, but it’s better than most Americans who do fake southern accents.

So why would Roth break the mould? He told Fancast that it was because it would be “overkill” to take on such a big role while also dealing with the accent challenge. Meier thinks that Roth is being too modest about his ability to do accents, but agrees that “performing an American role is an extra level of work for a British actor, whether or not he or she is great at it.” To keep up their accents, most actors need constant practice; nobody wants to become a laughingstock like Dick Van Dyke in Mary Poppins. But if an actor is always trying to make sure his accent is perfect, that can theoretically detract from the energy of his performance. Maybe Christian Bale wouldn’t have been so cranky on the set of Terminator: Salvation if he’d been able to use his native Welsh accent.

Though the writers of Lie to Me rarely acknowledge Dr. Lightman’s nationality—his daughter (Hayley McFarland) is American, and no one comments on the apparent culture clash—having a foreign-sounding hero may present some advantages. It helps keep the show from seeming too much like a retread of House and other shows about quirky geniuses. Dr. Lightman is similar to House, but at least his accent suggests a different cultural background. And seeing a stuffy British guy outsmart younger, clueless Americans gives Lie to Me a dynamic that other procedurals don’t have; it makes him seem like a nerdier James Bond. If audiences like it when Bond makes Felix Leiter look like a fool, why shouldn’t they like it with Tim Roth?

There are a few other signs that sounding British might no longer be a TV taboo. In the hit miniseries John Adams, star Paul Giamatti used a British accent to play the title character. This is historically accurate, but it’s still unusual; as Meier points out, “it’s hard to recall a movie about the American Revolution in which anyone but the British baddies sports a British accent.” But there’s still a long way to go before the British in Hollywood are allowed to drop their accents and come out of hiding. Meier notes that British actors are still routinely asked to “lose the accent,” as if American casting directors believe that “underneath the pretense, that actor really is American if he would simply ’fess up.” So for now, Dr. Lightman is alone as a TV hero who doesn’t talk American. Unless you count Simon Cowell as the hero of American Idol.