Islamic State militants are planning "indiscriminate attacks" on UK citizens on a scale similar to those perpetrated by the IRA 40 years ago, the new terrorism watchdog has said.
Max Hill QC, the new Independent Reviewer of Terrorism Legislation, warned that Islamists were targeting UK cities and said there was an "enormous ongoing risk which none of us can ignore".
But Mr Hill, who successfully prosecuted the failed 7/12 bombers, praised the intelligence services' "truly remarkable" success rate for foiling plots since the 2005 London bombings.
Speaking in his first interview in the role, Mr Hill told the Sunday Telegraph: "I think the intensity and the potential frequency of the serious plot planning - with a view to indiscriminate attacks on innocent civilians of whatever race or colour in metropolitan areas - represents an enormous ongoing risk that none of us can ignore.
"So I think that there is undoubtedly significant ongoing risk which is at least as great as the threat to London in the 70s when the IRA were active on the mainland."
Mr Hill questioned whether the fall of ISIS strongholds in the Middle East will cause British extremists to return to the UK.
"Of course the imminent fall of Mosul and perhaps the prospective retaking of Raqqa are both bound to lead to a higher instance of returning fighters. Does that mean that the British public need to be immediately alarmed at a spike in terrorist activity within this country?" he said.
"The answer to that is, I don't know, but it doesn't follow as a matter of fact that those who chose to go to live or fight abroad will bring that fight back to this country."