The British accent in the video that depicted the despicable and cowardly murder of an American journalist has raised concerns in the UK about the background of the ISIS jihadist. The Washington Post’s report on the butchery includes this nugget that should have Americans thinking twice, too:

In an interview with the BBC, Foreign Secretary Philip Hammond acknowledged that the apparent executioner spoke with a British accent and said the video seemed to be genuine.

Hundreds of Britons are believed to have traveled to Syria to fight in the country’s civil war, including many who have joined the Islamic State.

“We’re absolutely aware that there are significant numbers of British nationals involved in terrible crimes, probably in the commission of atrocities,” Hammond said. “Many of these people may seek at some point to return to the U.K., and they would then pose a direct threat to our domestic security.”

A European intelligence official said the British government was examining the video, and the speech of the purported executioner, to compare it with former Guantanamo Bay prisoners and other British residents believed to have joined the Islamic State.

Both prisoners in the video are wearing orange shirts and pants, similar to orange jumpsuits worn by detainees at the U.S. military prison at Guantanamo Bay, Cuba. A similar outfit, believed to be a jihadist symbol of the prison, was worn by Nicholas Berg, an American businessman kidnapped in Iraq in 2004 whose execution by an Islamic State precursor organization was recorded on video and posted online.

The May 2004 Berg killing was conducted by Abu Musab al-Zarqawi, the leader of Tawhid wal-Jihad at the beginning of the 2003 Iraq war, which became al-Qaeda in Iraq (AQI) at around the time of that beheading. US forces killed Zarqawi in an American airstrike, but AQI survived his death and the Anbar Awakening (if barely) to morph into ISIS when the US pulled out of Iraq. Berg was not the only American beheaded by Zarqawi, either; he also killed Owen Eugene Armstrong later in the same year, and both Berg and Armstrong wore orange jumpsuits when murdered, as did James Foley.

The orange jumpsuits are obviously referencing Guantanamo Bay, but the British seem concerned that there’s more than just symbolism now in play with ISIS. The US began releasing British subjects from Gitmo during the Bush administration under international pressure to shut down the facility, as well as releasing other detainees to their home countries, all of whom pledged to ensure that they would not return to the fight. We’ve seen plenty of recidivism since then, and all to this same end — to rejoin the jihad against the West and the nations in this region, and to recruit others to do the same.

It won’t be a surprise if the jihadist turns out to be a former Gitmo detainee, but it is a bit of a surprise that the UK doesn’t keep a close enough watch on those former detainees to account for their whereabouts immediately. After all, they have already been identified as threats, picked up in the battle zones far from home, which is how they ended up in Gitmo in the first place. The bigger worry for the UK — and for the US and other Western nations — will be how many of these butchers will make it back home undetected and anonymous. It should also have us taking great care not to release those who still present a danger, especially since we’re now desperately looking for ways to roll back ISIS. Perhaps we shouldn’t provide them more fighters than they already have.