OK, the very first scene where the Earth is about to be destroyed and Pro. Vogon Gents is telling the Earth creatures that the plans had been at Alpha Centuri... that whole sequence! Think about it. How could the Earth creatures understand what P.V.G. was saying without every single person having a babel fish? We know that the people understood what he was saying as P.V.G. kept answering the people. I mean I guess there could have been a loud speaker translator, however, wouldn't it have been activated when Ford and Arthur hitched a ride?