An operation run by GCHQ, the British intelligence and security organisation, used interception warrants to monitor phones owned by individuals linked to the plot, according to the Independent Reviewer of Terrorism Legislation.

Their agents’ analyses resulted in the identification of a cell that was close to carrying out their plan, it added.

The report provides several case studies of how anti-terror laws have been used, including how GCHQ “monitor[ed] the activity of a senior al-Qaeda leader and his network in a Middle Eastern country”.

GCHQ also provided support to both MI5 and European partners and helped to follow up 1,600 international leads, in the form of telephone numbers, email addresses and other identifiers, in the days following the Paris attacks, according to the report.

Powers enabling the mass interception of communications were also used to help a ground operations in Afghanistan.