Benedict Cumberbatch says being the voice of Smaug in second instalment of 'The Hobbit' was ''impossible''.

The 37-year-old actor has been cast as the sinister dragon in 'The Hobbit:The Desolation Of Smaug', which is Peter Jackson's big screen adaptation of J.R.R. Tolkien's beloved classic.

Cumberbatch found the role challenging since he had to capture the essence of a character which he cannot relate to.

He told the Yorkshire Evening Post newspaper: ''I was trying to articulate certain things which are impossible, because I'm a mammal trying to be a reptile.''

Cumberbatch physically portrays the dragon, which has been re-worked using CGI technology, and claims the Smaug represents ''corruption of power''.

He explained: ''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.''

Cumberbatch reunites with former co-star Martin Freeman who plays male lead Bilbo Baggins in the project. The pair previously worked together on BBC One series 'Sherlock'.