Benedict Cumberbatch found it difficult to voice The Grinch because he had to work by himself.

Benedict Cumberbatch

Benedict Cumberbatch

The 42-year-old actor brings to life the Christmas hating titular character in the upcoming Illumination Entertainment animated film - based on the 1957 Dr. Seuss book 'How the Grinch Stole Christmas!' - and he has admitted that he "got stuck on a couple of things" as being alone in the recording booth is a "very peculiar process" for him.

Speaking about the part on UK TV show 'Lorraine', he said: "I was literally in a wee booth by myself. No other cast members. It's a very peculiar process. Which can be a little bit insane. You can get stuck on a couple of phrasing... [you think], 'Surely you've got this by now!' "

Although it is a festive film, the 'Sherlock' star is certain his own children - Christopher, three, and one-year-old Hal, who he has with wife Sophie Hunter - will watch the film repeatedly not matter what time of year it is.

Referring to his kids watching it over and over again, he said: "It only dawned on me yesterday when people said, 'You do realise it's a Christmas movie'. [I thought] 'Oh yeah, this will have a life beyond this Christmas.' "

The 'Doctor Strange' actor also opened up about the new moustache he is sporting for an upcoming role in an upcoming thriller called 'Ironbark' - in which he portrays a spy called Greville Wynne - and the star admitted that he doesn't often get to "choose his own style of facial hair" as it is determined by the roles he takes on.

He said: "I very rarely get to choose my own style of facial hair, or hair, for that matter. It's all paid for kind of. It's all kind of designed for a look for a part.

"This is a man called Greville Wynne. It's more than just a moustache. [It's an] extraordinary true story about a man who became one of our main key sources of information during the Cuban Missile Crisis."