The Times Machines

Now there's a novel idea:
The invention of time machines in the future causes chaos as every man, woman, Dick and Harry and their respective dogs travel back in time to claim great works of art as their own. Further expansion of this rather insipid idea would be to have an organised group of Government art officials go back in time to prevent all the stupid vain plagiarism. It soon gets out of control as meticulously preserved billion year old copies copies of Great Expectations by Harold Green pop up in archaeological digs. As a result, people stop placing value on art and the world explodes.