Britiske sikkerhetsmyndigheter tegner et stadig mørkere bilde av situasjonen med hjemvendte Syria-krigere. Fredag ble antallet justert opp fra 400 til 500.

Politiet har arrestert 65 krigere det siste halvannet år, men bare de siste tre månedene har man arrestert 40. Det sier noe om takten.

Å overvåke alle jihadistene er en umulig oppgave, sier tidligere leder av MI6, Richard Barrett.

Richard Barrett, a former head of counter-terrorism at MI6, estimated that «possibly up to 300 people have come back to the UK» already, and warned that intelligence services faced an «impossible» task in trying to track them.

He told The Independent on Sunday: «If you imagine what it would cost to really look at 300 people in depth, clearly it would be completely impossible to do that, probably impossible even at a third of that number.»

Mr Barrett said police and intelligence resources were stretched in terms of numbers and knowing where the returning jihadists are.

He said: «With this whole business in Syria, although there is no linear projection from foreign fighters to domestic terrorists, it’s inevitable that a number will fall into this category.»

Mr Barrett has co-authored a report, released this month, which concludes that more than 12,000 foreign fighters have gone to Syria since the war began, and that it is «likely to be an incubator for a new generation of terrorists».

12.000 krigere er et meget høyt tall, og verden har ikke helt tatt inn over seg hva det vil få å si, for Midtøsten og landene de kommer fra.

Cressida Dick, the Metropolitan Police’s assistant commissioner and head of specialist operations, warned that Britain would feel long-term consequences of the conflict.

She told the BBC it represented a terrorist threat to the UK, and that young British Muslims who have travelled to the war-torn country to fight might commit violence when they return.

Ms Dick told BBC Radio 4’s The World This Weekend: «I’m afraid I believe that we will be living with the consequences of Syria – from a terrorist point of view, let alone the world, geopolitical consequences – for many, many, many years to come.»