who decides which members of the royal family attend foreign events such as other royal weddings? Does the Order of Precedence dictate what order people will get offered the position of representing the Queen and they decide if they want to go or pass on the opportunity?
At the Investiture of King Willem-Alexander in Amsterdam we saw a large group of "equals" and usually we would say: HIH comes before HRH. And then HRH comes before HSH. Inside these three "levels" the anciennity of the Reign is leading. This would lead to the following list:
HIH 1989
The Crown Prince of Japan (Naruhito)
The Crown Princess of Japan (Masako)
HRH 1946
The Crown Prince of Thailand (Maha Vajiralonkorn)
Princess Sirindhorn of Thailand (his sister)
HRH 1952
The Prince of Wales (Charles)
The Duchess of Cornwall (Camilla)
HRH 1972
The Crown Prince of Denmark (Frederik)
The Crown Princess of Denmark (Mary)
HRH 1973
The Crown Princess of Sweden (Victoria)
Prince Daniel of Sweden, Duke of Västergotland
HRH 1975
The Prince of Asturias (Felipe)
The Princess of Asturias (Letizia)
HRH 1989
The Crown Prince of Japan (Naruhito)
The Crown Princess of Japan (Masako)
HRH 1991
The Crown Prince of Norway (Haakon Magnus)
The Crown Princess of Norway (Mette-Marit)
HRH 1993
The Duke of Brabant (Philippe)
The Duchess of Brabant (Mathilde)
HRH 2000
The Hereditary Grand-Duke of Luxembourg (Guillaume)
The Hereditary Grand-Duchess of Luxembourg (Stéphanie)
HSH 1989
The Hereditary Prince of Liechtenstein (Aloïs)
The Hereditary Princess of Liechtenstein (Sophie)
Etc. Etc. (HSH The Prince of Monaco ranked before them, HRH The Princess Lalla Salma of Morocco ranked before them too, like The Sheikha Mozah, etc.)
In reality we saw at the Investiture that more or less the Order of Precedence is followed but that the royals themselves handle it relaxed. Of course the Crown Prince of Thailand is near the Prince of Wales, but in Amsterdam it was visible they were relaxed whether Maha Vajiralongkorn has to walk before or after Charles. Also Felipe (1975) really could not care less if he came before or after Victoria (1973). So there was a relaxed attitude to it and it worked wonders. No rigid policy in Amsterdam. I have the idea, looking at the wedding of William and Catherine, that this rigidness has also left the British Court. Also there is some relaxed attitude as well.