A 26-year-old man has been arrested on suspicion of terrorism offences, police said.
Firearms officers were drafted in for the arrest in north-west London at around 7.30pm on Tuesday as a precautionary measure, Scotland Yard said.
The man was arrested on suspicion of being involved in the commission, preparation and instigation of terrorism and remains in custody at a south London police station.
Police said no shots were fired during the operation.