Homeland star David Harewood has revealed he and his fellow British co-stars speak to each other almost constantly in US accents throughout filming for the TV hit.
He and show colleagues Damian Lewis and Rupert Friend have an "unspoken rule" that they keep up their voices even when they are chatting to each other when the cameras stop rolling.
The actors have had such convincing accents in the security thriller series that many American viewers have assumed they hail from the US.
David, soon to be seen in the second run of the show, said: "It's quite extraordinary - all three of the British actors have almost an unspoken rule that nobody's ever mentioned - we nearly always stay in our American accents when we're at work.
"Damian'll come to work and I'll be like 'Hey, man, how's it goin'?'. And he doesn't look at me and say 'What the f*** are you talking like that for?' - it's just unspoken."
He went on: "Every now and again one might drop out of accent and talk about the Olympics, or about something political that happens in the country, like the riots last year, when you have to get out of the accent.
"But most of the time you just forget, it becomes second nature."
Homeland returns to Channel 4 on Sunday.