... The unified model for Seyfert galaxies critically depends upon the existence of a geometrically and optically thick dust torus surrounding the AGN core. ... But evidence has been accumulating which points to the existence of thick dusty tori in AGN. ... We know that f / f discriminates between Seyfert 2 galaxies with and without polarised broad lines, presumably due to the dust torus being optically thick for wavelengths m, indicating that this ratio is tied in with the temperature of the hot dust. ...