Penultimate scene - the Police crowd outside Pym's hide-out: when the camera pans along Brotherhood's car and we see Mary sitting inside we hear a blackbird singing - faint, but clearly enough. I often hear blackbirds sing in the night, but that's in the summer - and far more northerly (5-600 km's) than Devon. I think it's only Paul McCartney having heard it in the dead of the night.