Iraq and Syria extremists could return to UK, Met chief warns
Hundreds of British extremists who have travelled to Iraq and Syria could return to the UK if jihadist groups start to lose the battles they are involved in, the Metropolitan Police commissioner has warned.
Sir Bernard Hogan Howe said the prospect of the extremists returning was his "biggest concern".
An estimated 500 Britons have travelled to Syria to fight in its civil war.
Sir Bernard said he could not predict when they would choose to return.
In a briefing with journalists, he said there were "a significant number of people who run the risk of being radicalised, militarised and potentially desensitised to violence, who one day we assume will come home".
World events were "moving at pace", he said, pointing to the progress made by the militant group Islamic State (IS) in seizing large parts of northern Iraq.
"If there were to be a reverse of that at pace, and they were to lose, there is a risk that hundreds of people would want to come home.
"That's the biggest challenge.
"We can't predict when it might happen. Should there be large numbers returning it puts great pressure on all of us to make sure that we are kept safe."
Tracking British jihadists fighting in Syria is believed to be the biggest priority currently for MI5.
Most of the Britons who have travelled to fight in the Middle East are believed to be in Syria. But last week a man from the UK told the BBC he had recently gone to Iraq to be at the "forefront" of the conflict there.
Sir Bernard added: "While they are there they are not an immediate threat, but should they come back, and should they come back together, that's a concern.
"We are trying our best to prepare for that. No-one should underestimate the task."