The fears of homegrown Islamic extremism striking the streets of England were heightened recently by the gruesome video of the beheading of James Foley, a US journalist murdered by a British Islamic State (IS, formerly ISIS) terrorist in Syria.

That British IS jihadist is far from alone in the ranks of the extremist group that has conquered large portions of Iraq and Syria, declaring itself early last month as a caliphate. According to the UK's Home Office, 500 people associated with Britain have joined IS, and roughly half have returned to the UK.

Khalid Mahmood, a British MP based in Birmingham, estimates that in total at least 1,500 young British Muslims have been recruited by extremists fighting in Iraq and Syria in the last three years.

Two British IS fighters currently in Syria, Abu Bakr and Abu Anwar, were interviewed via a video feed by CNN as reported on Thursday, and revealed that the video of Foley's horrific murder is acting as a recruitment video.

Abu Anwar said he would be "more than honored" to conduct a beheading like that of Foley, adding "I hope that Allah gives me a chance to do to James Foley to another enemy. My hands are ready to commit to this blessed act."

Evidently the two British terrorists do not intend to limit their actions to Syria. The two previously spoke to CNN, and at that time Abu Bakar said he would never go back to the UK.

Now Abu Bakar apparently has changed his mind, saying "I am ready to take that step to come back if your armies, your countries don't stop attacking us."

The UK has been on alert for the danger of jihadists returning from Syria for a while. 

Last October, MI5 Chief Andrew Parker warned "that there are several thousand Islamist extremists here who see the British public as a legitimate target." That threat was illustrated earlier last May, when a 25-year-old British soldier was brutally beheaded by Muslims in the middle of a London street.

Indicating the level of the British threat, the CIA sent a special contingent of agents in June to investigate the extent of Islamic extremism in the UK, in a snub to British intelligence agencies.