personaly I do not allways Like the way he work's but i would imagine that he did not go back in time because the ministry had it in their possesion, and if he did ask to use it then he would have been told no because that would mean that V would be alive and well, which would be bad for everone. It just sucks when you have to choose between the lessor of two evils. I also believe their are laws to how you can use a time device, it can not be for life changing events or anything.