Poirot star David Suchet revealed he has to relearn the Agatha Christie character's voice each time - despite playing him for two decades.
The actor admitted he pops on DVDs to remind him how to play the part of the Belgian detective.
Suchet, who will be seen as the sleuth in Appointment With Death on UTV on Christmas Day, told the Radio Times Christmas issue he watches his old shows for hours to perfect it each time.
He said: "It's odd, I've been working on his voice for 20 years, but every time I play him I have to find it again.
"Having played half a dozen characters in the interim I'll wonder 'where's this little man?' - so I put on the DVDs and sit with my wife and we watch for hours.
"Then I rehearse the voice and the walk to remind myself of him. It's a discipline getting him exactly right."
He even maintains the accent between takes, he told the magazine. "It's not an actor's affectation. It's purely to help me."
Appointment With Death is his 61st starring role as Poirot, having first tackled the role in 1989 in The Adventure Of The Clapham Cook and originally contracted for just one season.
"I was originally contracted for one season with an option on a second," he says, fat-suit and accent shed for lunch in his trailer.
He is hopeful that in the near future he may complete Christie's full complement of Poirots.
"That would be a wonderful thing to achieve. When we come to the last story, where Hastings sees Poirot as a frail, little old man in a wheelchair, that will be it.
"My Poirot will have come to an end. If they do remakes, fine, and I wish the actor who plays him all the luck in the world. I'll feel enormous sadness that as an actor I will have to put him in his coffin and bury him."
© Press Association