A story I will probably never write

because it would take too much research.

A Neonazi group develops a time machine. They send an agent back to a school in South London to kill a schoolboy, because eliminating this individual would, by itself, give Germany a far better chance of winning WWII

Agent carries out mission and returns to base. Nothing has changed.

Boss: You idiot! You killed the wrong boy!

Agent: What do you mean? I killed Jones.

Boss: You were supposed to kill R.V. Jones!