Vatican Cameos means: Sherlock Holmes from BBC Sherlock shouts Vatican Cameos at John Watson after he has finished opening Irene Adler’s vault. He then realizes that it is a booby trap. Holmes will give Watson a cue when they are in danger so he can know how to respond. They call it their “safe word.” (in Community Dictionary, added by Isaias Collier)

What else does Vatican Cameos mean?

  • It is a reference to Sir Arthur Conan Doyle’s story. In which Conan Doyle refers back to another Sherlock Holmes case that he worked on regarding some Vatican Cameos. It is code for duck in the BBC Sherlock case, which means get out of my way. This is probably a reference to another Sherlock-Watson case that Watson did not show in the episode. In this instance, Watson knew to duck away from an approaching bullet. Cumberbitches use it most often. (in Community Dictionary, added by Reddow2Heyday)
  • “Vatican Cameos” is the phrase that Sherlock uses to describe Irene Adler as she opens Irene’s safe. This phrase was first used in World War 2. The phrase was first used to describe a person who entered a British military base with a knife or gun. This phrase signalled that everyone should duck from the fire. Sherlock was aware that John would recognize the phrase and move out of harm’s way to get the gun from the safe. This isn’t a safe phrase that Sherlock and John co-ordinated. It’s very clever, I think. (in Community Dictionary, added by Marcos Aguilar)