A man has been arrested at Heathrow Airport on suspicion of a terrorism offence, the Metropolitan Police said.
The 39-year-old man was arrested on Saturday on suspicion of possessing terrorist-related material under Section 58 of the Terrorism Act 2000.
Police said he was arrested under PACE legislation after arriving at the airport and has been taken to a west London police station where he remains in custody.
Officers from the Met's Counter Terrorism Command are investigating the matter.