I am a little bit confused by the variety in dresscode. It seems the Vatican has not sent invitations and everyone was free to come to the Piazza San Pietro.
Military tenue with Orders HRH The Prince of Asturias
Civil formal tenue with Orders HRH The Prince of Orange (Also the Spanish PM and the Netherlands Ambassador to the Holy See wore this, but not the Dutch PM, very weird)
Jacquet HSH The Prince of Monaco
Daily suit-and-tie with Orders HRH The Duke of Gloucester
Daily suit-and-tie HM The King of the Belgians HRH The Grand Duke of Luxembourg HSH The Hereditary Prince of Liechtenstein
I thought it was messy. This can happen without a clear invitation policy. Two ladies whom held the privilège du blanc: Queen Paola and Grand Duchess María Teresa. All ladies submitted themselves to the black/white protocol while not needed (no invitation policy). I liked that. The jewels were as expected: understated diamonds, pearls or nothing.