"I didn't feel any pressure is the honest truth. At least I didn't feel Bilbo pressure but I felt the pressure that I always feel in that I want to be good," he said.
While The Hobbit may be his biggest film role to date, Martin admitted that he tries to remain pragmatic about the future.
"I try not to expect anything because there is no guarantee of anything at all. I've been told before, 'Your life's going to change after this comes out'. No it didn't, it didn't change," he said.
"Obviously this is a huge film but any premature expectation or patting on the back is a very dangerous thing to do because it can only come with disappointment."
While JRR Tolkien's novels are beloved by children and adults, Martin admitted he only read the novel two years ago.
"I just didn't grow up with it. I'm a fan now and see what it's about but it just wasn't in my universe then," explained the British actor.
:: The Hobbit is out now.