Britain launched the largest security response since 7/7 last night as counter terrorism sources revealed up to 450 radicalised Britons have returned to the UK from Syria.
Special forces were deployed on the streets to monitor stations, shopping centres and key pubic places amid fears the UK could be the next target for an Isil terror outrage.
Personnel from the elite Special Reconnaissance Regiment (SRR) were backing up undercover armed police officers to protect the UK in the wake of the Paris massacre.
It can also be disclosed that Scotland Yard is currently investigating 600 terror cases related to Syria and Iraq.