A woman feared to have been planning to travel to Syria with her four children is being questioned by police after returning to Britain.
Zahera Tariq, 33, was held on suspicion of child abduction at Luton Airport on Thursday night, police said.
Tariq was detained in Turkey on Tuesday after the family went missing from their home in Walthamstow, north-east London, last week.
They were believed to have flown from London City Airport to Amsterdam on August 25.
All of the children were said to be ''safe and well'' when the group was detained by Turkish authorities.
A Metropolitan Police spokesman said Tariq had been arrested by officers from the force's Counter Terrorism Command (SO15).
A family court judge will make decisions about the long-term futures of the children who are aged between four and 12.
Mr Justice Cobb today analysed developments in the case at a private hearing in the Family Division of the High Court in London.
He said detail of proceedings could not be reported but he said the youngsters had been taken into foster care for the "time being" - and were together.
The judge praised the way British police had worked with Turkish authorities to ensure the children's safe return.
And he said it was right that the public should be told that a judge was overseeing family court litigation and would decide what was in the youngsters' best interests.