Britain's intelligence agency, the MI5, downgraded the country's terrorist threat level from "severe" to a "substantial" on Monday.
MI5's Joint Terrorism Analysis Centre (JTAC) considers the risk of a terrorist attack as likely when the threat level is "substantial," and highly likely when it is "severe," the second-highest rating. The assessment considers terrorist threats from right-wing and left-wing political factions, Northern Ireland, and radical Islamist groups.
The highest rating is "critical," where an attack is highly likely in the near future. MI5 has raised the threat level to "critical" four times since the ratings were first established in 2006.
Two of those times where in 2017, when Islamic extremists carried out four major attacks which killed 36 people in total.
The level was first raised from "substantial' to "severe" in August 2014 due to the rise of the Islamic State group in Syria and Iraq.
While most of the UK's terror level has decreased, Northern Ireland has remained at a "severe" risk since 2010, when terror threats from Northern Ireland were recorded separately.
The potential of a "no-deal Brexit" leading to a hard-border between the UK-controlled Northern Ireland and the Republic of Ireland, which will remain in the EU, has aggravated tensions in the island's political climate.