For that shot I lay the camera on its back on the floor and used the self timer to take 5 shots at 0.5sec intervals. 1 stop apart. Last time I did that was in Ely Cathedral and caused quite a stir. I was shooting with the Nikon 14-24mm at 14mm - so you need to be a way off the avoid being in the shot. So I put the camera down, pressed the button, and ran. The security on duty thought I'd planted a bomb! Ooops!
This time I explained to the lady in a big red frock exactly what I was about to do