Ahmed Walid Rashidi, a Danish aid worker, was one of the lucky few to be released by the Islamic State after being held captive for a month. He told the Sunday Times that the majority of foreign fighters have British or German accents. The town of Manbij in northern Syria was like a "little London or a little Berlin".
Britain's intelligence services estimate around 500 British-born Muslims have been radicalised and travelled to the Middle East to join the Islamic State in Iraq and the Levant (ISIL) terrorist group.
But it could be three times as much as that, according to Syrian political activist Danni Maki, who is researching Middle Eastern extremist groups. "It's very difficult to document the numbers going to Syria, the smallest number could be up to 700 but people also suggest 1,000 and other reports suggest 2,000, so we know that it's now between 1,000 and 2,000", says Maki.
Manbij and rural areas surrounding Aleppo are, according to Maki, so densely populated with foreign fighters that it's changing the demographics of the country and pushing large numbers of the original Syrian population out.
"Many of these areas inhabited with ISIS in the north of Syria have a large foreign population which has taken the original Syrians out of the picture and created a new society", says Danni Maki. "There are up to 8,000 families who have moved from the West to Raqqa which has made a huge change on the dynamics on the area. It's a reality in northern Syria unfortunately.
‘Little London', the area claimed to be heavily populated with British Jihadis, is not far away from the border with Turkey, which according to Maki is why it is popular with European fighters. He says it's no surprise the area is home to the majority of English speaking foreign Jihadis.
"The UK has one of the largest numbers of jihadi fighters in Syria who have committed some of the worst atrocities in Syria which has sent tremors through Westminster. Britain has the worst rate in the whole of Europe for the number of foreign fighters in Syria."
But Maki says it's the return of these British Jihadis that pose the greatest threat to the UK. "Even more dangerous is that 250 of these extremists have already returned. This is creating real fear in the security services in the UK. Not long ago we saw three Britons making an ISIS video and this became a huge media storm which reflects the growing fear that the radicalisation and extremism in Syria and Iraq will manifest in the UK on the streets in the future", says Maki.
He is not alone in suggesting that the fallout of further radicalisation of British Jihadis will be felt on the streets in Britain. Former head of London's Metropolitan Police Counter Terrorism Unit, Cressida Dick, had also warned that the consequences of the war in Syria would be felt in Britain for years to come.