Colin Firth just can't stop talking, according to his King's Speech co-star Helena Bonham Carter.
"I did find it funny that as soon as the camera was turned on he'd have difficulty speaking [playing a stammerer] but as soon as it's off, honestly, he just talks for Britain!" she laughed.
The film, which sees Colin play King George VI, traces the monarch's impromptu ascension to the throne and his work with a speech therapist (played by Geoffrey Rush).
"They talk non-stop so it was kind of hard to concentrate," Helena said of working with the pair.
She laughed: "They're both amazing - they should have their own chat show!"
The King's Speech is released in cinemas on Friday, January 7.