Indeed, he did. I assume because Prince Rainier wanted to observe the tradition to which I referred.

Close relatives of all (?) the independent hereditary monarchies each represented their own ruler. The only monarchs who attended in person, I think I am correct in saying, were the rulers of British protectorates, eg. the Malayan and Brunei Sultans, Queen Salote (of blessed memory), and some Middle Eastern Sheikhs and Emirs.