Question about incidental music in an 'Olympus' bit

I was wondering about the piece of music played in one of the Olympus sketches. It is right at the start of a scene which starts with a superimposed caption saying "Apollo's temple" after which a person painting a vase (Mel Smith) yells to the people in the room that they should keep still, meaning they are the motif of the vase. It is a classical piece which I have heard before, but I don't know the name of it. It has a sort of imperial flow to it, with strings and brass. I know it is a difficult question, but could anyone help me identify the piece in question?