A tank was needed for Steven Spielburg's movie "War Horse", and finding a real one was possible, but after 80 years the machines were pretty delicate. Something more durable was needed, and Neil Corbould's special effects team were enlisted. Vince Abbott was tasked with designing and building the tank. His video of photographs he took during the build speak for themselves. Starting with a used excavator, and measurements from a real Mk IV, his scratchbuilt version slowly came together in about ten weeks. After the movie was over, Bovington's Tank Museum acquired the tank in 2012 for their programs, giving the real ones a well deserved rest.
From Vince Abbott's YouTube channel