A man has been arrested at Standsted Airport on suspicion he planned to travel to Syria.
The 37-year-old, who has not been identified, was detained by counter-terrorism police before boarding a flight to Turkey on Tuesday evening.
He was arrested on suspicion of preparing for acts of terrorism and is being held at a south London police station.
Officers are searching two residential addresses in the north of the city.
Scotland Yard said his arrest was not connected to the Manchester Arena attack on Monday.