HOW SECURITY SERVICES PRIORITISE THREAT POSED BY TERROR SUSPECTS

Security services attempting to contain the unprecedented terror threat must assess the potential danger posed by the thousands of individuals on their radar.

Scrutiny of the processes used to decide where to focus resources has intensified after the disclosure that one of the London Bridge attackers was known to authorities.

MI5 adopts a “triage” process for incoming threat intelligence and a prioritisation system which is regularly reviewed.

Officials assess leads for links to existing investigations, and if there are connections these are forwarded to the relevant team.

Where they do not relate to inquiries that are ongoing, leads are tested for credibility and a new probe is launched where appropriate.

Investigations are given a priority according to the risk they carry. There are understood to be four broad categories:

Priority 1: Investigations into individuals or networks where there is “credible and actionable” intelligence of attack planning

Priority 2: High- and medium-risk activity, such as a serious intent to travel overseas and fight or undertake terrorist training

Priority 3: Uncorroborated intelligence, where further action is needed to determine whether a threat exists

Priority 4: Individuals who have previously posed a serious threat to national security, who are not currently deemed to be involved in such activities, but where there is a risk of “re-engagement”

There are no strict rules for what resources are given to a particular investigation, with actions taken according to whether they are necessary and proportionate, and on the “balance of risk” in other probes.

Priority levels are regularly tested and can be changed where there are shifts in activities or aspirations among those being monitored.

Targets will be prioritised according to their position or importance within most probes.

These can fall into three tiers: the main targets of an investigation; key contacts of the main targets; and contacts of tier 1 and 2 targets who are likely to be involved only in marginal aspects of activities.