The arrest of two men last week on terrorism charges relating to Syria reveals just how serious the issue of foreign fighters has become. Estimates suggest that up to 366 young Muslims from the UK might now be participating in the Syrian conflict.

There is a multiplicity of problems here. Aside from the obvious fears about young men training with terrorist organisations, the global jihadist movement is currently enjoying an unprecedented rebirth. Its membership is being replenished and it is not overstating the case to suggest al-Qaeda affiliates now control greater territory than they ever have in the past.

It is tempting to turn a Nelsonian eye to the phenomenon. There is a view in some parts that radicalised young men should simply be allowed to leave the country and die in Syria. This misunderstands the problem. Most of those who leave won’t fight until the end. Many will return and it will be impossible to detect them all.

The Home Secretary should therefore extend greater powers to the UK Borders Agency, Police, and Security Service to stop and investigate potential foreign fighters before they leave the country. Present measures are insufficient and crude, relying on Royal Prerogative to strip suspects of their passports. What should replace it is a legislative approach which establishes clear procedures and allows for judicial oversight.

Terrorism studies have shown the problem to be a generational one. With the death of Osama bin Laden and Anwar al-Awlaki in 2011 there was a sense that the jihadist threat which began with those who confronted the Soviet Union in Afghanistan was finally in remission. Syria has now revived its fortunes by another generation. Introducing robust measures to stop and prosecute potential suspects before they leave this country will better insulate us against its repercussions in the years ahead.

Shiraz Maher is a Senior Research Fellow and Head of Outreach at the International Centre for the Study of Radicalisation (ICSR) at Kings College London

Tags: Afghanistan, Al Qaeda, Anwar al-Awlaki, Osama bin Laden, Theresa May, UK Borders Agency