Watch Benedict Cumberbatch film his Smaug motion capture performance in The Hobbit

The Sherlock star played the giant evil dragon in The Desolation of Smaug

Benedict Cumberbatch films his performance as Smaug in The Hobbit: The Desolation of Smaug (YouTube)

Benedict Cumberbatch fans have been treated to a clip of the actor filming his motion capture performance as The Hobbit's evil dragon, Smaug.

The Sherlock star plays the giant Lonely Mountain lizard in The Desolation of Smaug but to create the character in all its menacing glory, he had to writhe around in a technological sensor suit and helmet.

Behind-the-scenes footage shows Cumberbatch lying on the floor and threatening an unseen Bilbo Baggins, the hobbit hired by Thorin to help the dwarves reclaim their stolen kingdom and gold.

"Well, thief! I smell you. I hear your breath. I feel your air. Where are you?" he snarls, as his movements and dramatic facial expressions are recorded to assist the visual effects team.

"You kind of have to imagine yourself into a vast creature in a huge space when you're really crawling about on a grey bit of carpet," said Cumberbatch, who was mentored by pioneering actor Andy Serkis.

Serkis, known for his performances as Gollum in The Lord of the Rings and Caesar in The Planet of the Apes, told Cumberbatch to "treat it like playing the role and go in there physically" instead of just providing the voice.

"We were looking for an actor who was not just going to voice a dragon that we would imagine," added director Peter Jackson.

"We wanted someone who would do something original and unexpected, something that was a surprise to us."

The video was released as part of the movie's extended edition, available for digital download today and in stores from 3 November.