It is not a question of finding 1 extra chair. If the heir + spouse from Denmark are there. Suddenly you would have to invite all the other heirs + their spouses, in order to treat all the royal houses equally
Not exactly so. As you say, Frederik was invited as his mom is a widow. However, if I am not mistaken, this is the only Euro royalty invitation where a married couple are split: one on the royal invitation list, one not. (Who does that?!) Worse, the wording was such on the invite that there was need for an apology for the misunderstanding. No doubt if actually brought up the chain of command to King Charles’ attention, he’d have likely told them to make room to avoid any embarrassment.
420