Not sure that the full effect is visible here in the file, so I may need to post the original.
Anyway, was playing as you do with B&W conversion and wondered what happened if you blended a B&W layer with the original. So 60% B&W (Tri Max 100 sim.) blended Multiply.
19:30 - Version 2 now added. Obviously I cropped slightly to reduce the effect of the person popping in to frame bottom left on V1, so not exactly the same composition, but close enough to see the difference in colouring.