Ramping up to Doctor Who Series 6, the BBC has released a 2-minute prequel to the first episode, The Impossible Astronaut. Not a preview, a PREQUEL. I'll wait while you watch.
Done? Ok, so what does it tell us? Though the creepy aliens and desert environment seen in the previews might have put us in mind for a 1940s or 50s Roswell story, the president here looks to be Nixon. I'm going by the nose more than the voice (sorry, Nixon actor!). So late 60s, early 70s then. Moffat returns to the trope of creepy child voices because, hey, it's the creep that keeps on creeping.
Man, whoever listened to the Watergate tapes in the Whoniverse must have gotten a chill!