A 16-year-old boy has been arrested on suspicion of possession of an imitation firearm, the Metropolitan Police has said.
The teenager was arrested on in Fulham Broadway at around 14:40 BST on Saturday and was believed to be on his way to a comic book convention, the police said.
Officers had received reports about a boy “displaying a weapon and walking towards a crowded area”.
No one was injured in the incident and the teenager remains in police custody.