Benedict Cumberbatch found voicing Smaug in The Hobbit: The Desolation of Smaug difficult as he 'is a mammal trying to be a reptile'.

The Sherlock star plays the dragon Smaug in the second instalment of the Hobbit series and he told the Yorkshire Evening Post, "I was trying to articulate certain things which are impossible because I'm a mammal trying to be a reptile."

On his character he added, "Smaug is the ultimate symbol of the corruption of power. He's a sleepy serpent on top of his pile of gold. It brings him nothing but a damp, dank retirement, no joy or humour. He's vainglorious and proud of his own power and wealth, but it has essentially ruined him."

The Hobbit: The Desolation of Smaug is out this week on December 13.