After a long discussion, the BD was decreed ok as it met three tests - was not intrusive (into the passenger space), did not obstruct entry/exit, and did not obstruct (rear) vision. These tests were apparently (IIRC) laid down in some RTA (I assume) document, possibly the advice they provide to workshops doing the inspections. The BD is still in the car, and nothing has since been said (I am careful to always take it to the same workshop for the inspection, and they have never done any work on my cars - strictly inspection only). The BD does not have the CAMS sticker.
