I think they knew and that is probably why the honeymoon was postponed.
I have seen posts from people watching the wedding that thought there was an undercurrent.
Given that Britain now seems to be a Muslim State..they could have worried about what would take place.
I bet there were a lot of discussions to the US asking for this announcement to be postponed until after the wedding.
Obama still had all day to announce this.
No doubt wait until after the wedding. Am betting that Will and Kate are now in a “safe place” ala our VP. Both Will and Harry are airforce and will no doubt report to duty tomorrow.
There was a post the other day about the Muzzies dropping their planned protest of the wedding because they said some big attack or something was coming.