I laughed. You were meant to laugh. The Bishop invited people to laugh by what he said and how he said it. Especially when he said "I will sit down, we gotta get you all married" I laughed out loud. It's not inappropriate to laugh at a wedding when celebrating love and joy. Also the few times when we thought it was over the bishop went on speaking made me, and people in the chapel, laugh.
The many comments about Zara Tindall looking shocked during the sermon are based on one capture of her and taken out of context. Her daughter were born a month after the wedding and Zara was visibly uncomfortable in the wooden pews during large parts of the service.