Through the door is the lower gallery. You need to find De La Serre now who is somewhere in this area. Head West and go up the stairs in front of you. This leads to the first of 2 viewing galleries that you need to go over. Head up to the railing and look over it. You will not see see him in the crowd below or up on the dais. Check then head for the far stairs and take them over to the other side. Avoid investigating the crowd as it is a waste of time.
Head over to the far end of the second viewing gallery. Look over the dais at the far end. Look toward the throne. You will find De Le Serra.