An aeroplane passenger was arrested at Heathrow Airport on suspicion of being involved in the commission, preparation and instigation of acts of terrorism - and a female companion was later arrested for the same thing at an address in north-west London.

Officers from the Metropolitan Police's Counter Terrorism Command (SO15) were acting upon intelligence when they stopped a 26-year-old woman at Terminal 5 at Heathrow Airport as she was preparing to embark on a flight to Istanbul, Turkey, at 9.20am yesterday.

She was subsequently arrested on suspicion of being involved in the commission, preparation and instigation of acts of terrorism. A large quantity of cash was also seized.

The second woman, a 27-year-old, was arrested later the same day at 2.25pm also on suspicion of being involved in the commission, preparation and instigation of acts of terrorism at an address in north-west London. She was taken to a London police station where she remains in custody.

A police statement said: "Both arrests were intelligence-led and not in response to any immediate threat or risk. Detectives are currently searching two addresses in north and north-west London under Terrorism Act. Inquiries are at an early stage and we are unable to give further detail at present."