A 30-year-old man has been arrested on suspicion of "being concerned in the commission, preparation or instigation of acts of terrorism".
Officers from the Metropolitan Police's counter-terrorism command arrested the man at an address in north London on Wednesday morning.
Scotland Yard said: "He has been arrested and detained under Section 40(1) of the Terrorism Act 2000, on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism.
"He is at present in custody at a central London police station and officers are searching a residential address in north London. Inquiries continue."