You don't know what the protocol is anymore than I do, all you're saying is that what happened 'is the protocol'. Yet the protocol is distinctly different to Charles and Diana's wedding. A so-called protocol that says invite tin pot entertainers but not ex-PMs. The protocol is defined by whatever those who made it up this time wanted it to be.
You're arguing is that protocol can be just made up as you go along and modified on a whim as seen fit on an event by event basis. That's not protocol that's BS.
How many times do I have to say this Charles and Diana's wedding was a full state occasion. Charles is the immediate heir to the throne. William and Kate's wedding was a semi-state occasion he is not the immediate heir to the throne.
Because this was not a full state occasion the protocol does not require ex-PM's be invited it was therefore left up to to William and Kate. Kate organised a great deal of what happened maybe it was her that decided. I have no doubt that if William was next in line in the order of succession both Blair and brown would have got a invite but he is not