Stuart Milligan's spent the majority of his career in Britain, though. I was told my (albeit eclectic) Yank accent started breaking down after only about six months over there. (Also, I have never heard a believable Richard Nixon impression. Anyone who attempts it always ends up sounding like Jimmy Durante.)

*gives the clip another listen* I dunno...to my ears, it's definitely an American accent the kid is trying to do. Especially the 'it doesn't matter' line: ie, a very British child trying their darndest to soften the consonant, and not quite getting there. Plus, why would Amelia call the Doctor "the Space Man"?

Side note: please tell me I'm not the only one who scoffed upon hearing the "no monsters in the Oval Office" line and thought several very cynical thoughts about previous administrations?