A joint military and police operation in Newcastle, in northern England, thwarted a probable ISIS terrorist plot.

Members of the United Kingdom Special Forces (UKSF) and police officers from the Counter Terrorism Command (CTC) assaulted a house in Arthur’s Hill and arrested an individual suspected of plotting a terrorist attack for Christmas. The suspect, a 33-years-old male, whose name hasn’t been released by the British law enforcement authorities, was taken for questioning in a nearby police department. He is suspected of the “commission, preparation, or instigation of acts of terrorism.”

“They were dressed like soldiers and had guns — it is armed response,” said a man to a local newspaper. “They told us to come up here and evacuated the street.”

The CT response team surrounded the suspect’s house and stormed in, catching the man unawares. Thereafter, they swept the area to ensure that there weren’t any improvised explosive devices (IEDs) implanted. Regular police officers visited nearby businesses and schools to reassure the population.

Emerging reports indicate that this was a pre-planned operation. A representative from the North East Counter Terrorism Unit stated that the man had been under surveillance for some time before the operation took place. The investigation was a joint effort by the police and the MI5, Britain’s domestic security service — a rough equivalent of the FBI.

The UKSF is comprised of the Special Air Service (SAS), the Special Boat Service (SBS), the Special Reconnaissance Regiment (SRR), and the Special Forces Support Group (SFSG). Although the UK Police have dedicated counter-terrorism units — officers serving in such outfits are designated as Counter Terrorism Specialist Firearms Officers (CTSFO) — serious terrorism cases are usually assigned to the UKSF. For example, following the Manchester Concert bombing, which claimed the lives of 22 people and wounded 139, it was the UKSF that responded.

Since the repeated attacks of 2017, the threat level for a terrorist attack is at “Severe.” Last year, the U.K. suffered four attacks (Westminster Bridge, Manchester, and London Bridge). In a recent report, the U.K. government stated that there are more than 700 active counter-terrorism investigations (with about 600 related to Islamist-inspired plots and 100 related to the far-right).

Following the deadly 2015 Paris attacks, the British government formed an unofficial, secretive 70-man counterterrorism unit. Comprised of SAS and SBS operators, alongside support personnel, the unit is tasked with constant, no-notice counterterrorism duties. They are supported by the UK Army Air Corps’ (AAC) 658 Squadron.