On a flying visit to London a while ago I snapped the exterior of the former Midland Grand Hotel, George Gilbert Scott's recently restored Victorian Gothic pile, now the St. Pancras Renaissance Hotel. Last week I was staying there so I was able to explore beyond the massive façade, and here - for your delectation - is the famed staircase (once used by The Spice Girls, even).
For any non-UK readers puzzling over the title of this post, it's an expression of surprise or amazement, and not unjustified in this context.