The UK national threat level from terrorism is severe. The threat level for Northern Ireland-related terrorism in Northern Ireland is substantial. Neither changed this week, and neither has changed for months, so the value in checking them today is in understanding what they actually describe.
The gov.uk page states the position in two sentences: "The threat to the UK (England, Wales, Scotland and Northern Ireland) from terrorism is severe" and "The threat to Northern Ireland from Northern Ireland-related terrorism is substantial". It sets out five levels: low means an attack is highly unlikely, moderate means an attack is possible but not likely, substantial means an attack is likely, severe means an attack is highly likely, and critical means an attack is highly likely in the near future. The page also notes that "Threat levels do not have an expiry date. They can change at any time as different information becomes available."
One practical point about that page: it carries no date. It states the current levels and says nothing about when they were set, so anyone dating a level from that page alone is guessing. The dates come from separate announcements.
The Joint Terrorism Analysis Centre raised the national level on 30 April 2026. A GOV.UK announcement published the following day reads: "The Joint Terrorism Analysis Centre (JTAC) yesterday (30 April 2026) raised the UK National Threat Level from SUBSTANTIAL, meaning an attack is likely, to SEVERE, meaning an attack is highly likely." The announcement said the increase came after the stabbing in Golders Green in north London "but it is not solely a result of that attack", and pointed to a rising Islamist and Extreme Right Wing threat from individuals and small groups based in the UK. The Northern Ireland level was lowered on 6 March 2024, when MI5 moved it from severe, meaning an attack is highly likely, to substantial, meaning an attack is likely.
There is no separately published figure for Northern Ireland-related terrorism in Great Britain, and this is where working memory tends to be out of date. Since 23 July 2019 there has been "a single national threat level describing the threat to the UK", with the threat from Northern Ireland-related terrorism in Northern Ireland remaining separate. MI5's own guidance states that "There are two published threat levels", and that "The national terrorism threat level covers all forms of terrorism aside from Northern Ireland-related terrorism in Northern Ireland". Northern Ireland-related risk in Great Britain therefore sits inside the national severe figure. It is not a number you can look up on its own, and a client asking for it should be told that rather than given a figure from memory.
Keep one definition straight, because two official wordings are in circulation. The gov.uk scale defines severe as "an attack is highly likely", with no time period attached. The Security Minister's statement of 14 May 2026 attaches one: "'Severe' means that a terrorist attack is highly likely in the next six months." Use the scale page for the definition and attribute the six month horizon to that statement rather than blending them. The same statement records that the level was last at severe from November 2021 until February 2022, and that the system itself is under review: "I have also initiated a review of the national threat level system, which currently captures only the threat from terrorism, to ensure that it remains fully relevant, and that we are communicating as clearly as possible with the public about the national security threats that we face today."
For operators, severe is a statement about likelihood with no named target, so it should drive general hardening rather than principal-specific measures. Treat route and venue reconnaissance as live work rather than an archived file, rehearse arrival and departure choke points, and make sure venue duties are written down and evidenced. For anyone working in Northern Ireland, substantial is a separate and lower assessment that has held since March 2024, and conflating it with the national figure will mislead a client in one direction or the other.
