The tube station (or perhaps just the entrance near the shopping centre?) was also closed. While passing on the bus at about 17:45, I noticed through the closed gates that the info board said it was closed "for safety reasons". All of the three bus stops in front of the shopping centre were taped off too.
I checked on the TfL website after getting home and there was no mention of a station closure or any disruption to tubes or buses at E&C.
So do we know which building is causing all the trouble?
Could "unsafe building" feasibly mean that a building is deemed unsafe because of an incident from the previous evening? Or does "unsafe building" really mean that a building itself is structurally unsafe?
The link does actually say "unsafe structure" so I assume it is in fact a structural problem...
The fact that the police tape extends further this morning than it did yesterday (the whole southbound carriageway now bwing closed, rather than just the pavement and bus stops) would support this, if something's in danger of collapse.