She had just got off a flight from Istanbul, Turkey
British police have arrested a 21-year-old woman on suspicion of terrorism offences.
She was detained on Thursday evening just after 9.00pm by officers at Heathrow Airport.
Police say she had just got off a flight from Istanbul, Turkey.
The woman, who is from north London, was arrested on suspicion of preparation of acts of terrorism.
She has been taken to a London police station where she is being detained.
Searches have also been carried out at two addresses in the north of the city.
Officers say the arrest "is Syria-related".