Everytime I walk over London Bridge a building catches my eye. Its probably not the one you are thinking of here. Most people would be hurting their neck looking up at the Shard or pointing their camera at Tpwer Bridge of which both you can see here. I always look at the cube shaped building at the end of the bridge.
I have no idea what is inside it part from guessing that it is an office building. If anyone knows please leave a comment on ti as it would be great to know. It looks like it has a chunk missing from the centre, adding a huge column to support the top heavy structure.
Very strange indeed.