The Duchess of Cambridge – who looked amazing in a recycled Alexander McQueen ensemble - just 26 days after giving birth – was caught by several Twitter users appearing to snigger along with her step mother-in-law, the Duchess of Cornwall.
And what was the reason for the usually composed Duchess’ stifled laugh?
Perhaps it was Bishop Michael Curry’s scene-stealing sermon, or perhaps it was just nerves.
Guess we’ll never know!
However, Kate wasn't the only royal caught misbehaving at the wedding...
Even Prince Harry didn't seem able to keep a straight face.
Elton John's face said it all.
Camilla's reaction is priceless!