A man and a woman have been detained by specialist officers at Heathrow Airport on the suspicion of "the commission, preparation or instigation of acts of terrorism".
It's understood that the couple were arrested after arriving on a flight into the airport.
Police are searching two separate addresses in East London as part of their inquiry.
"The arrests form part of an investigation into travel to Syria in support of alleged terrorist activity."
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Monday night's weather for the east of the region
Monday night's weather for the west of the region