My building has an intercom system which is linked to the tv so you can see who's ringing the bell. I was expecting S and T any minute because S had just called to make sure she remembered the number of the flat so I buzzed them in. I watched her on the camera using body language to someone in the lobby that she couldn't get in, that the intercom wasn't working. Whoever it was refused to let them in, eventhough he was clearly on the other side of the glass door and it would have taken absolutely no effort.
When they finally did come up I asked what happened and she said that the man kept saying he wasn't a doorman. S and T are Bengali locals. The man was a 50something white local. We all knew without saying it that the man was being hostile because they are Bengali. We talked around it. But we never mentioned the real reason, our suspicion, that he was a white racist who refused to open the door for a Bengali. Maybe because we didn't actually say it, the incident stayed with us all day.