An unfortunate paradox prevents this....if it happened, then there would be no reason in the future or present to go back in time to prevent it, thus no one would go back in time to prevent it so it wouldn't happen then it would, or wouldn't....ow my head hurts. Stupid time travel with its grandfather and novikov paradoxes
For clarity ...lets say HTT goes back and stops Mike Ashley being born, there's no Mike Ashley running Newcastle now, so HTT decides not to go back in time to get rid of Mike Ashley, so he doesn't do it, and then all of a sudden there's a Mike Ashley again.
Too much temporal physics for one day
That's not how BTTF worked though, so we're all good.