Damian Lewis Says He Plays American Characters So Often He Forgets to Speak in a British Accent

— -- Damian Lewis says he's been playing American characters for so long that sometimes he forgets to speak in his British accent.

"I go get my groceries in an American accent," Lewis said in an interview with Peter Travers on ABC News' "Popcorn with Peter Travers." "And I get halfway through paying and I'm like, 'I'm so sorry. I'm British, and I have no idea why I'm talking in an American accent to you but I've been doing it all week."

While most people know him as the American characters Bobby Axelrod on the Showtime show "Billions" and Nicholas Brody in another Showtime show "Homeland," Lewis can finally speak in his British accent in his latest film "Our Kind of Traitor."

In the movie, Lewis plays the British character Hector, who works for the British secret intelligence service MI6 and has a grudge against a politician who's done something unspeakable to him and his family.

"Hector himself is a man who worked in the city and left the city and the world of high finance, I think, impatient with its corruption, its implicit corruption, and the way in which the free market is only interested in generating money," Lewis explained. "So he goes to MI6 and he finds himself really the same person there too: a voice against authority, and something of a maverick."

Lewis stars in the film with Ewan McGregor and Naomi Harris, whose characters work with Hector to investigate the Russian mafia and try to help a Russian man's family safely escape Russia.

"[Hector] sees an opportunity to get back at this corrupt politician who he had wanted to exact revenge on for many, many years," Lewis said. "And ... over the course of the film ... he's finally moved by the plight of this family and the children and finds himself tangled by affairs of the heart."

Through his career, Lewis has become a recognizable actor in the U.S., and he credits his role as Richard Winters in the 2001 TV mini-series "Band of Brothers" with helping him achieve stardom.

Lewis said meeting the series' director Steven Spielberg and star Tom Hanks for the first time was "thrilling."

"They'd flown me all the way to Hollywood and here I am staying at Shutters on the Beach [hotel] with a view of the ocean with this five-star treatment," Lewis recalled. "And I’d been in the Royal Shakespeare Company wearing tights the year before and this is a long way. I thought, 'This is amazing.'"

Lewis said he's been fortunate to play both British and American characters throughout his career.

"When they came to make 'Band of Brothers' in the U.K., they snapped up the tax incentives which meant that they were beholden to those incentives. They had to use a certain amount of British crew," Lewis explained. "And in that process, I got lucky. I was one of the guys cast in that role."

He added, "I think that's what's happened. It's just the net widened. The ambition grew. And they started bringing in actors, talent, crew just from all over the place. And I got lucky."

Watch the full interview with Damian Lewis with Peter Travers on ABC News' "Popcorn With Peter Travers" above.