I know this is not strictly DIY but perhaps someone who's seen a lot of bathrooms might know what's caused this weird mark on the chrome in my hand basin. It's circular, which suggests a pool of something has been sitting there but I can't think what. Also, there's nothing to feel with a fingertip - the chrome is smooth to the touch all over. Vinegar/baking soda have had no effect.
Many thanks for any suggestions offered.
Many thanks for any suggestions offered.