Three British teenagers who were stopped from travelling to Syria from Turkey and arrested have been released on bail, Scotland Yard says.
Two boys aged 17 from north-west London and a man aged 19 were flown back to the UK on Saturday night, the Met said.
They were arrested on suspicion of preparing terrorist acts and have been bailed pending further inquiries.
UK police alerted Turkish officials after a tip off from the younger teenagers' parents, the Times has said.
Scotland Yard said counter-terrorism officers were initially made aware that the two 17-year-old boys had gone missing and were believed to be travelling to Syria on Friday.
The parents of the boys contacted police when the pair did not return home after Friday prayers, according to the Times.
Further enquiries revealed they had travelled with a third man, UK police said.'Security co-operation'
"Officers alerted the Turkish authorities who were able to intercept all three males, preventing travel to Syria," a police spokesman added.
They were returned to the UK at about 23:10 GMT on Saturday and were arrested by counter-terrorism officers.
They have been bailed to return to a central London police station pending further enquiries.
The trio had flown to Istanbul from Barcelona, in Spain, a Turkish official told the BBC.
The two 17 year olds were stopped at Istanbul's Sabiha Gokcen airport by Turkish authorities acting on intelligence provided by British police about the pair.
However, the 19-year-old man was only detained after being questioning by Turkish police, the official said. He was also arrested at the airport.
"This is a good and a clear example of how the security cooperation between Western intelligence agencies and Turkey should work," the official added.
BBC correspondent Andy Moore said the development came after "recriminations" between UK police and Turkish officials following the disappearance of three London schoolgirls.
Shamima Begum, Amira Abase, both 15, and Kadiza Sultana, 16 - all from London - took flights to Istanbul last month, from where it is feared they travelled to join Islamic State (IS) militants in Syria.
Their disappearance led to criticisms from Turkey's deputy prime minister, who said officials in the country had not been given enough warning about their disappearance.
"On this occasion it seems that the warning was raised in the UK and that was communicated very quickly to Turkey," our correspondent said.'Britons of interest'
The BBC's Selin Girit, in Instanbul, said the deportation of the two 17-year-old boys and 19-year-old man shows that when Turkish police have information "they can co-operate".
"When the three UK schoolgirls went missing Turkish officials said 'it is not us to blame because we were not passed the information of these missing girls. How can we find and locate and deport them when we do not have the necessary information?'," she said.
"But this shows when there is a co-operation between intelligence services, between police, Turkish police can act accordingly."
The Home Office says there are about 600 Britons "of interest" in Syria.
The BBC understands about 100 Western volunteers - including some Britons - are fighting as part of the 30,000-strong Kurdish forces against IS, while more than 500 Britons are believed to have travelled to join IS militants.