Greg Cox wrote:
Spock was surprised as anybody else when T'Pring actually chose the challenge option.
While there was no reason for Spock to suspect at the time he beamed down, when the bridal party entered he could have begun to realize.
First official clue would have been the presence of Stonn. I think that it was fairly obvious that the original plan was that he was to be the champion. Everyone else in the bridal party had a role or duty. Why was Stonn walking in?
Second clue might have been to entrance of the weapons carriers, while it might be tradition to alway have weapon present, I do wonder if they are only brought if there is a anticipation of combat.
It might have not been the biggest of secrets (except to Spock) that T'Pring was going to contest the marriage.
My assumption is that the presence of weapons was (usually) ceremonial, as when, say, the Queen of England knights someone or when a military honor guard carries sabers or rifles at a funeral or whatever. Nobody is expecting actual combat!
(I was actually walking the dog by our local cemetery the other day when I was startled by gunfire. Turns out there was a military funeral going on.)
As for Stonn, Spock brought two guests to the ceremony, so why shouldn't T'Pring? For all Spock knew, Stonn was just a close friend or colleague of T'Pring's who was there to share this moment with her. It's not like Spock was up to date on her personal life.