The terrorism threat level in Northern Ireland has been lowered from “severe” to “substantial” for the first time in 12 years after what the government described as significant continuous progress with peace. The Northern Ireland secretary, Brandon Lewis, announced the decision after an assessment by M15. “This is the first time the threat level in Northern Ireland has changed since 2010 and shows the significant progress that Northern Ireland has made, and continues to make, towards a more peaceful, more prosperous and safer society. “It is a testament to the ongoing commitment to protecting the peace process and tackling Northern Ireland-related terrorism, and the tremendous efforts of the Police Service of Northern Ireland and MI5 for their hard won gains over the past decade,” he said. The threat level is subject to continuous review, and judgments about the threat are based on a wide range of information. This was the first time the threat level in Northern Ireland has been reduced from severe since it was first published in 2010. Substantial means that a terrorist attack is likely and may well occur without further warning. Lewis warned however that the lowering of the level did not mean all threats had gone away. Dissident republican groups such as the New IRA still exist. It admitted responsibility for the murder of the journalist Lyra McKee in Derry, three years ago. On Sunday, her grieving family accused dissidents of insulting them by planning to stage a commemoration parade next month on the anniversary of her death on Easter Monday. The Northern Ireland secretary said: “It is not a time for complacency. There is still a minority who wish to cause harm in Northern Ireland. “As ever, the public should remain vigilant and report any concerns they may have to the police.” “Dissident republican terrorist activity has been at a lower level in Northern Ireland in recent years and security services have secured a number of successes disrupting the activities of the terrorist organisations.” A file was sent to the Public Prosecution Service (PPS) in relation to a 26-year-old man arrested last Tuesday in connection with the young journalist’s murder. Five other men questioned by detectives about the killing were released without charge. Tensions have also flared in the past year over the impact of the Northern Ireland protocol, with violence spilling out on to the streets last April in loyalist and nationalist interface areas. Buses have also been hijacked and set alight but this violence is not categorised as a severe or critical threat of a terrorist attack. There are five levels of threat: low – an attack is highly unlikely; moderate – an attack is possible but not likely; substantial – an attack is likely; severe – an attack is highly likely; and critical – an attack is highly likely in the near future. The level is set by the Joint Terrorism Analysis Centre (JTAC) and MI5. Threat levels do not have an expiry date. They can change at any time as different information becomes available.