The rooftops in Mary Poppins weren't authentic either . And the soot on the faces of the chimney sweeps probably wasn't real soot atall. The movie is a fantasy , a pantomine .That's the way I look at it anyway and I find Van Dyke's fake cockney accent absolutely charming . I don't think Tommy Steele could have done much better; does anyone remember him singing Little White Bull? I doubt if it will ever make to the digitrad