Counter terrorism police have arrested an 18-year-old woman at Stansted Airport on suspicion of terrorism offences.
The teenager was arrested as she arrived on a flight at around 4pm on Friday (16 January) and was taken to a central London police station for questioning.
She was arrested on suspicion of the preparation of terrorist acts and membership of a banned organisation. The arrest is linked to 'foreign terrorism'.
While it is not yet clear where she was travelling from, it has been reported that the woman flew back to the UK 'using a circuitous route.'
The arrest is being directly linked to an earlier anti-terror raid in Hackney, London last year, where a 21-year-old man was detained on suspicion of assisting another person to commit acts of terrorism and facilitating their travel to Syria.
He was arrested on October 29 in a dawn raid and questioned at a south London police station. A search at the residential address in Hackney was also carried out by the Metropolitan Police's anti-terror command. He was rebailed to a date in January.
Counter-terrorism experts in the UK have expressed growing concerns relating to the escalating numbers of militarised fighters returning home.
Speaking earlier today, Britain's senior anti-terrorism police man, assistant commissioner Mark Rowley said there were 327 arrests for terrorism offences in the UK last year - and increase of one-third on 2013.
"Last summer, the national threat level was raised to SEVERE. This means a terrorist attack here is highly likely," he explained. "At that time we took a number of additional steps to protect communities and the public. This included, but was by no means limited to, additional armed patrols and more visible policing. We also held a counter-terrorism awareness week before Christmas to alert the public to the need for greater vigilance, and we offered specific advice where necessary.
"But, in light of the attacks in Paris last week, we have been reviewing, alongside our partners, our overall security posture. This is a further step in a process over a number of years of learning lessons from such events.
"For example, since the attack in Mumbai in 2008, we have enhanced our ability to respond effectively to a marauding terrorist attack by expanding our specialist firearms capability and improving the effectiveness of the response and joint working of all the emergency services. More generally we have continued to refine our plans and to enhance our capabilities to respond to a terrorist threat which has evolved and diversified."
Assistant Commissioner Rowley said that as a result of greater public awareness the number of calls to the anti-terror hotline has increased "significantly" over the past few months making "an important contribution" to keeping the public safe.