I'm always being asked where I'm from. Often I'm asked if I'm British, although I suspect that's more to do with the way I tend to talk, little archaic word usages, etc., rather than any affected accent. I got over the Monty Python phase at age 14, as we all did.
My vowels do sometimes drag out a bit, I confess. But that's just an inordinate fondness for Dorothy Parker more than anything. However, I have indeed carefully and deliberately cultivated an almost perfectly accentless form of English, and for a reason. My mother is from the South, and growing up I talked more like her than I did my D.C.-bred father. My British passengers joke about how their accents win them a free pass here; people think they're brilliant. With a Southern accent, it's the opposite. When a Southern passenger rides with me for more than five minutes, oh, it comes back with a vengeance.
My passenger tonight notices the change over the course of our long ride, and asks about it. Sheepishly, I explain. He laughs and tells me a great story. He's a lawyer from Alabama. He lets his accent run "thick as molasses" all through the trial, because it "lulls the other side into thinking I'm an idiot. They raise fewer objections; they just get downright sloppy." Then for the summation, the voice he acquired when graduating cum laude from Georgetown comes out. Wham.
"I'll bet you've got a terrific case record," I say.
"Best in all of Alabama, sweetheart."