Do you think the part of the trailer with Lestrade in 221B is most likely from Mount Stuart Square because of how blue the skull painting is?
Hmmm. It does look particularly blue in this shot of Greg, doesn’t it?
It could just be a trick of the lighting. Or it absolutely could be related to filming at Mount Stuart Square. I don’t think it was actually filmed there, as we didn’t see Rupert there. Also at Mount Stuart Square there were only two walls–let’s call them the front and back walls–and not the green side walls. In the scene with Greg, you can clearly see the side wall, so I’m pretty certain this had to have been filmed on the actual set. But as I said, it definitely could be connected. Maybe the street scene transitions into the real 221B, which is where we then see this shot of Greg.