The United Kingdom downgraded its national terrorism threat level from "severe" to "substantial" on Monday — its lowest level since 2014, Interior Minister Priti Patel said. 

"Despite the change in the threat level, terrorism remains one of the most direct and immediate risks to our national security," Patel said in a statement.

The threat level has been categorized as "severe" for most of the past five years — though in 2017 it was upgraded to "critical" on two brief occasions, indicating that an attack was highly likely in the near future. 

Read more: 'Terrorists will never succeed': defiant Londoners gather in show of strength

The downgrade means that the UK now sees an attack as likely rather than highly likely.

In that year, the UK experienced four attacks which killed 36 people, the deadliest of which took place at the end of an Ariana Grande concert in Manchester in which 22 people died. Other attacks took place near the Houses of Commons in Westminster and at London Bridge.

The "substantial" threat level continues to indicate a high level of threat and an attack could take place without further warning, said Patel. 

mmc/aw (Reuters, AP)

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