A man who was seen carrying a weapon and wearing a bulletproof vest on a Tube train in central London turned out to be an employee of a "laser tag" game firm in his work outfit.
Armed officers were called to Waterloo underground station during Wednesday morning's rush hour when a passer-by expressed concern.
But the "weapon" was actually a laser gun and was part of the man's work kit.
British Transport Police said he had been spoken to "very sternly".
Officers tracked down the man after studying CCTV images from the station and gave him "words of advice" about his actions, it is understood.