Removing dash air vents

Hi all
Can someone please tell me the secret of how to get the round air vents out from each end of the dash on my series 1. I refer to BD37801 and BD33160. Is 33160 a large threaded nut which unscrews from behind the 37801 vent? I can’t move the piece at the back separately from the front piece, The the whole thing rotates. I cant tell how it works from looking at the parts book, page 25-08.

Any help appreciated.

Ian

As you presume but a bayonet arrangement similar to a taillight bulb. They tend to stick. Hold the front to keep it from rotating.

Thanks Robert, got it, was just very tightly jammed.

Ian