It's huge and it's metal. Really, really tall and quite long. It doesn't look like a normal building. I'm not so sure where about it is, but I think it was around half an hour before the coach got to Victoria Station and it probably came into London through the north and/or east.
Oh, and there were some important looking people in suits stood outside.
Anyhow, I really really want to know what it is. Suggestions? I'd be able to recognise it easily.