They must have had hidden cameras.
3 seconds sound clip from the A King in New York (1957) movie soundboard.
You can hear this line at 00:35:44 in the Blu-ray version of the movie.
Quote context
[...]
- After what I saw, Your Majesty, perhaps I am.
- I'm an idiot! I thought something peculiar was going on!
- They must have had hidden cameras.
- Outrageous. Sue them for damages!
- It's rather late, Your Majesty.
[...]