Although Peter Jackson is acting as producer and co-writer on the upcoming YA fantasy film Mortal Engines, that is not the only thing that has been keeping him busy lately. He has also been working on a unique WWI documentary called They Shall Not Grow Old, which takes old archival footage from The Great War and gives it a huge makeover by adding colour, sound effects, dialogue and, yes, even a 3D transfer. The goal was to create an accurate and immersive historical experience for modern audiences and as far as I know nothing quite like it has been attempted before. The movie already played in theatres and aired on the BBC in the U.K. but Warner Brothers and Fathom Events are presenting it in theatres in the U.S. next month for two days only. They Shall Not Grow Old hits select theatres on Dec. 17th and 27th; check out the trailer after the jump and see what you think.