State banquets also take place in the Ballroom; these formal dinners are held on the first evening of a state visit by a foreign head of state. On these occasions, for up to 170 guests in formal "white tie and decorations", including tiaras, the dining table is laid with the Grand Service, a collection of silver-gilt plate made in 1811 for the Prince of Wales, later George IV. The largest and most formal reception at Buckingham Palace takes place every November when the Queen entertains members of the diplomatic corps. On this grand occasion, all the state rooms are in use, as the royal family proceed through them, beginning at the great north doors of the Picture Gallery. As Nash had envisaged, all the large, double-mirrored doors stand open, reflecting the numerous crystal chandeliers and sconces, creating a deliberate optical illusion of space and light.