Britain's most senior counter-terrorism police officer says the country's security forces have prevented 13 planned terrorism attacks in less than four years, and are dealing with more than 500 investigations at any one time.
Mark Rowley, assistant commissioner for London's Metropolitan Police, says most of the information used by police and intelligence agencies to prevent attacks comes from the public. He says the terrorism threat to Britain remains "severe" - meaning a threat is "highly likely" - as authorities face "some big operational challenges."
Rowley also says military successes against the Islamic State group in Iraq and Syria will not "eradicate the terrorist problem" as the threat to Britain is broader than IS or Al-Qaeda and includes "extreme right-wing groups."
