A machine gun, a revolver and gun parts were found hidden beneath gnomes in a suburban back garden.
The weapons were wrapped in plastic and concealed under a paving slab surrounded by pot plants and the gnomes at an address in South Norwood, south east London, Scotland Yard said.
Officers found the stash - a MAC-10 machine gun and magazine, a Smith and Wesson .44 revolver and the barrel and cylinder for a Smith and Wesson .44 - when they raided the property in Warminster Square at around 11am yesterday.
Two men have been charged with three counts of possession of a firearm with intent to endanger life and will appear in court today, while a woman was arrested and bailed.
Detective Inspector Phil Holt, from the Met's Operation Trident gang crime command, said: "To the unsuspecting eye, there was nothing about the appearance of this garden that would suggest any criminality.
"Thanks to the fantastic work of our officers we were able to establish that, in fact, beneath the facade of respectability there was something far more sinister being concealed.
"As a result, three more weapons have been taken off our streets and out of the hands of those criminals that might intend to use them."