Right. Plus it's like the Doctor said in the Fires of Pompeii, there are things in history that are fixed events (like the volcano eruption) which can't be changed, but little things (like rescuing a family of four) is fine. What Harry here is doing is sticking his nose into major events which are pretty much fixed.

I don't want to spoil anything, but about Next Harry? Do you really think that this Jerk Stu is going to not get his way in any of this? >_