Two British teenagers arrested by anti-terror police in Kenya are back in Britain after having been deported today.
Both are expected to be closely questioned by police in the UK over fears that they had been radicalised by militant Islamists.
Mohamed Mohamed Abdallah, of Somali descent, and Iqbal Shahzad, of Pakistani descent, were arrested in Kenya at the weekend.
Both went missing from their homes in Cardiff, south Wales, more than a week ago.
Abdirhman Haji Abdallah, told today of his desperate dash to Kenya fearing son Mohamed planned to join Islamist rebel group al Shabab.
He met the authorities in Kenya, identifying the teenagers to the police and passing a photograph of his son to them.
Both teenagers, believed to be aged 18, were arrested before crossing the border into neighbouring Somalia.
They were escorted on to a plane in Nairobi, the capital of Kenya, at 9am local time and deported today.
Police have now revealed that both were under surveillance from the moment they arrived in Kenya.
Their movements were closely followed by Kenyan security forces as they travelled around the country.
Their counterparts in Britain are expected to take steps to satisfy themselves that the teenagers represent no threat to security here.
"They left for Britain this morning after being escorted on to a plane. They were not released but deported," said Charles Owino, deputy spokesman for the Kenyan police.
He said Kenya was concerned about potentially radicalised Islamists using the country as a "gateway" into Somalia.
He said the problem was a "severe concern" for the country and something which it takes very seriously.
As a result both teenagers were identified from their arrival in the country as a potential threat.
"They were under surveillance from the moment they got into the country," Mr Owino said.
"We had a lot of surveillance and intelligence on them but this sort of security is routine in the fight against terrorism."
He added that police in Britain may well wish to monitor the movements of the teenagers now they are back in the UK.
"That is something that will be up to Britain if it feels it should investigate this matter further. If it feels they pose a threat to Britain."
Mr Abdallah told the BBC Somali Service today that Kenyan police had arrested his son near the Somali-Kenya border at Lamu.
He flew into the country in a desperate attempt to stop him crossing into Somalia and believing his son had been misled.
"I thought that he was coming here to go to the war in Somalia," he said.
He said that he had since been allowed to see his son and described him as seeming "very happy."
He added: "Plus you do not feel guilty, because he is not guilty."
His intervention came as members of the Muslim community in Cardiff were contacting the UK authorities to communicate their fears.
The concerted efforts to head off both teenagers and prevent them making irrevocable mistakes have been praised.
Cardiff South and Penarth MP Alun Michael spoke of the action as a "positive" approach.
"The Muslim community became very concerned when they discovered that two young men had gone missing, one from a Somali background and one from a Pakistan background," he said.
"They are both quite young, about 17 or 18, and from what I have been told they are two bright, intelligent young men who have got their lives before them."
"It was an immensely positive meeting for a community that doesn't want to see the message of Islam distorted and are determined to provide a positive model for their young people," Mr Michael said.
"Everyone is relieved the two boys have been found."
South Wales Police declined to comment on the situation.