It was in The Hitchhikers Guide to the Galaxy, or in the series at least. His scenario was two warring planets sending out armadas to fight each other, but while they were on their way faster ships were created and sent so when they got there the battle was already over.
It's stolen from Elite: Dangerous. You can find a few of those colony ships drifting around deep space, but you're warned with heavy penalties to not interact with them, for this exact reason.
I mean fair, but the original ELITE was released in 1984 and is essentially the same science fiction universe. You're right though, it's not a new idea