It is the now familiar nightmare image. A kneeling prisoner, and behind him a black-hooded man speaking to camera. The standing man denounces the West and claims that his form of Islam is under attack. He then saws off the head of the hostage. Why did Wednesday morning’s video stand out? Because this time the captive was an American journalist —James Foley— and his murderer is speaking in an unmistakable London accent.

The revulsion with which this latest Islamist atrocity has been greeted is of course understandable. But it is also surprising. This is no one-off, certainly no anomaly. Rather it is the continuation of an entirely foreseeable trend. Britain has long been a global hub of terror export, so much so that senior US government officials have suggested the next attack on US soil is likely to come from UK citizens. All countries — from Australia to Scandinavia — now have a problem with Islamic extremists. But the world could be forgiven for suspecting that Britain has become the weak link in the international fight against jihadism. And they would be right. This is not even the first beheading of an American journalist to have been arranged by a British man from London.

In 2002, 27-year-old Omar Sheikh was in Pakistan. A north London-born graduate of a private school and the London School of Economics, he had gone to fight in the Balkans and Kashmir in the 1990s. In 1994 he was arrested and jailed for his involvement in the kidnapping of three Britons and an American in India. Released in 1999 in exchange for the passengers and crew of the hijacked Air India flight IC-814, he was subsequently connected to the bombing of an American cultural centre in Calcutta in January 2002 and that same month organised the kidnapping and beheading of the Wall Street Journal reporter Daniel Pearl.

Back then it was possible to dismiss Omar Sheikh as a one-off — a macabre fluke. His alma mater shrugged off concerns about the number of London-based students who had got involved in Islamic extremism or the radical preachers touring the country. The shrug became a little harder to maintain — though maintained it was — the next year when two British men — Asif Hanif, 21, from Hounslow in west London and Omar Khan Sharif, 27 — carried out a suicide bombing in a bar on the waterfront in Tel Aviv. Omar Sharif had been a student of King’s College London, just across the road from LSE. That time the glory of killing three Israelis and wounding over 50 was claimed by the terrorist group Hamas.

As the list of British-born jihadists grew, their activities also got closer to home. On 7 July 2005, British-born Muslims carried out the first suicide bombings on British soil, with four more attempted a fortnight later. On Christmas Day 2009, the former head of the Islamic Society at University College London attempted to explode a bomb on a plane as it landed in Detroit. Last year, two converts decapitated Drummer Lee Rigby in broad daylight in south London. It is important to keep in mind that these are just the most high-profile cases. But the list of cases which were thwarted by good security work or sheer luck is astonishing. As well as the constant stream of convictions, at least one large-scale mass atrocity attempt on the lives of the British public was thwarted each year. As were smaller attempts. Everybody still remembers the killing of Lee Rigby, but how many people recall the case of Parviz Khan’s Birmingham terrorist cell? Khan was convicted in 2008 for a plot the previous year to kidnap and behead a British Muslim soldier on video.

All the while, as the list of jihadists grew, so did the number of places where they could train. Perhaps as many as 4,000 people from Britain are thought to have gone to train or fight in Afghanistan. Estimates of the number of British citizens who have gone to fight in Syria and Iraq range from just over 500 to 1,500 (a figure from Khalid Mahmood, a Birmingham Labour MP). If the larger figure is correct, it would be significantly higher than the number of Muslims currently serving in Britain’s armed forces. Some of these jihadists have returned; some have been killed fighting. But it is now obvious that whether we like it or not, this is Britain’s problem.

Involvement in Syria spreads across Britain. As with other conflicts, a large proportion of the Brits going to fight in Syria appear to be — like the murderer of James Foley — from London. This is in line with other work, including a list of all terrorism convictions in the UK to date, which shows that almost half of Islamism-inspired terrorism offences and attacks on UK soil over the last decade were perpetrated by individuals living in London at the time of their arrest.

But involvement in the Syrian conflict has also spread to Birmingham and other places with large Muslim populations, as well as some places that will have surprised the wider public. In February of this year it transpired that the 41-year-old Abdul Waheed Majid from Crawley, West Sussex, had become a suicide bomber. On 6 February the non-Arabicspeaking Brit carried out a truck-bombing against a jail in Aleppo, Syria.

In May, the Instagram account of a British man believed to be from London shows other jihadist war crimes from Syria, including the killing of a prisoner believed to be a loyalist of President Bashar al-Assad. One of the people shooting bullets into their captive is identified as a British man who in another video berates British Muslims for not providing enough support to the jihad. ‘You know who you are,’ he says, ‘from the capital, the Midlands, up north, wherever you may be… it’s a disgrace, that brothers know where these wives are, where these families are, and yet you are buying your nephew or your child a PlayStation 4 or taking them out to Nando’s.’

The list goes on. A cell of young men from Cardiff. Others from Portsmouth. Earlier this month, Abdel-Majed Abdel Bary from west London appeared in a photo he himself posted on Twitter. He is pictured holding a severed head with the caption ‘chillin’ with my homie, or what’s left of him’. This is all part of the strange juncture that Syria has become for British jihadis — a meld of street cool, Islamic extremism and ultra-violence. Even the register in which these men communicate on social media is familiar. For instance Madhi Hassan, 19, from Portsmouth, sent out a media image of himself holding a jar of Nutella, to reassure Brits coming over that they would not lack all comforts.

Of course, one line of argument claims that if we just left all these places alone then none of this would come to us. But we left the Balkans alone and created one generation of jihadists. Then we didn’t leave Afghanistan and Iraq alone — and created another generation of jihadists. Now we have very much left Syria alone — and lo and behold, we seem to have created another jihadist generation. Damned if you do, damned if you don’t, apparently. Yet remarkably few people seem to realise that this isn’t really about us.

Nevertheless, it comes ever closer to home. In recent weeks the black flag of jihad as used by Isis has been flown openly in London — supporters of Isis have appeared on Oxford Street — and elsewhere. Just this week, the imam of a leading Welsh mosque resigned after a pro-Isis guest preacher was invited to speak at his mosque.

This battle is going on in households and mosques up and down this country. We fear joining up these dots. And we fear giving offence more than we fear the international opprobrium that is coming our way.

The country that brought liberty to much of the world is now exporting terrorism to large parts of it. Britain needs to look to itself, and address this problem, if there are not to be many more videos like this week’s.

Tags: Daniel Pearl, Hamas, Iraq, IS, ISIS, Islam, Islamic State, Islamism, Islamists, James Foley, jihad, Kashmir, Lee Rigby, London, Omar Sheikh, Pakistan, Parvis Khan, Radical Islam, Syria, Tel Aviv, Terrorism