A West London man in his late teens was "armed with a suspected firearm" and walked into a Park Royal bank on December 23, but was detained by armed police officers soon after.
Metropolitan Police said the man "entered and claimed to staff that he was in possession of a suspicious device in a rucksack bag."
"A suspected firearm was recovered - at this stage it is not believed to be genuine," a spokesperson for the Met Police said.
Footage was filmed by @FaridQureshi_UK.