Director Peter Jackson has told RTÉ TEN that the build-up to making his new movie The Hobbit: An Unexpected Journey was the toughest of his career.

With rights co-owners MGM originally unable to greenlight the project because of financial difficulties, the delays saw original director Guillermo del Toro leaving the project for other film commitments while Jackson also suffered a perforated ulcer.

Jackson told RTÉ TEN: "It was the toughest build-up. But, y'know, the irony of it was once we walked on the set and started shooting it was the smoothest shoot we've ever had. It was the most problem-free and happiest time on a film set ever. So I guess we got all of our bad stuff out of the way at the front."

You can watch RTÉ TEN's interview with Peter Jackson by clicking the link on your left.

Asked what caused him the most headaches when filming began, Jackson replied: "Our 13 dwarves [the Company of Dwarves, played by the likes of Richard Armitage, James Nesbitt and Aidan Turner] had so much make-up they had to wear. They had two or three hours [of make-up] in the morning, they had heavy costumes - fat suits - they had big rubber hands and huge feet and so they were physically kind of challenged. And suffering the whole time.

"I was very much aware as I was sitting there in my t-shirt and shorts on a hot set directing that they were suffering."

"I tried not to feel too sorry for them, though!" he joked.

The Hobbit: An Unexpected Journey opens in cinemas on Thursday.